MORGAN STANLEY DEAN WITTER BEST IDEAS PORTFOLIO OCTOBER 1997
S-6EL24, 1997-08-29
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<PAGE>


            Filer:  DEAN WITTER SELECT EQUITY TRUST

MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO OCTOBER
                             1997

              Investment Company Act No. 811-5065

              SECURITIES AND EXCHANGE COMMISSION
                    WASHINGTON, D.C.  20549

                           FORM S-6


For Registration Under the Securities Act of 1933 of Securities
of Unit Investment Trusts Registered on Form N-8B-2.


     A.  Exact name of Trust:

         DEAN WITTER SELECT EQUITY TRUST,
         MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO
         OCTOBER 1997

     B.  Name of Depositor:

         DEAN WITTER REYNOLDS INC.

     C.  Complete address of Depositor's principal executive office:

         DEAN WITTER REYNOLDS INC.
         Two World Trade Center
         New York, New York  10048

     D.  Name and complete address of agents for service:

         MR. MICHAEL D. BROWNE
         DEAN WITTER REYNOLDS INC.
         Unit Trust Department
         Two World Trade Center - 59th Floor
         New York, New York  10048

         Copy to:

         KENNETH W. ORCE, ESQ.
         CAHILL GORDON & REINDEL
         80 Pine Street
         New York, New York  10005


<PAGE>






     E.  Total and amount of securities being registered:

         An indefinite number of Units of Beneficial Interest pursu-
         ant to Rule 24f-2 promulgated under the Investment Company
         Act of 1940, as amended

     F.  Proposed maximum offering price to the public of the
         securities being registered:

         Indefinite

     G.  Amount of filing fee:

         N/A

     H.  Approximate date of proposed sale to public:

         AS SOON AS PRACTICABLE AFTER THE EFFECTIVE DATE OF THE
         REGISTRATION STATEMENT.

         The registrant hereby amends this Registration Statement on
         such date or dates as may be necessary to delay its effec-
         tive date until the registrant shall file a further amend-
         ment which specifically states that this Registration
         Statement shall thereafter become effective in accordance
         with Section 8(a) of the Securities Act of 1933 or until
         the Registration Statement shall become effective on such
         date as the Commission, acting pursuant to said Section
         8(a), may determine.
<PAGE>
               DEAN WITTER SELECT EQUITY TRUST,
MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO OCTOBER
                             1997

                     Cross Reference Sheet

            Pursuant to Rule 404(c) of Regulation C
               under the Securities Act of 1933

         (Form N-8B-2 Items required by Instruction 1
                 as to Prospectus on Form S-6)

Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

     I.  ORGANIZATION AND GENERAL INFORMATION

1.   (a)  Name of Trust                )  Front Cover
     (b)  Title of securities issued   )

2.   Name and address of Depositor     )  Table of Contents

3.   Name and address of Trustee       )  Table of Contents

4.   Name and address of principal     )  Table of Contents
     Underwriter                       )

5.   Organization of Trust             )  Introduction

6.   Execution and termination of      )  Introduction; Amendment
     Indenture                         )  and Termination of the
                                       )  Indenture

7.   Changes of name                   )  Included in Form
                                          N-8B-2

8.   Fiscal Year                       )  Included in Form
                                          N-8B-2

9.   Litigation                        )  *

     II.  GENERAL DESCRIPTION OF THE TRUST
          AND SECURITIES OF THE TRUST




- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

10.  General Information regarding     )
     Trust's Securities and Rights     )
     of Holders                        )

     (a)  Type of Securities           )  Rights of Unit Holders
          (Registered or Bearer)       )

     (b)  Type of Securities           )  Administration of the
          (Cumulative or Distribu-     )  Trust - Distribution
          tive)                        )

     (c)  Rights of Holders as to      )  Redemption; Public Offer-
          withdrawal or redemption     )  ing of Units -Secondary
                                       )  Market

     (d)  Rights of Holders as to      )  Public Offering of Units
          conversion, transfer, par-   )  - Secondary Market; Ex-
          tial redemption and simi-    )  change Option; Redemp-
          lar matters                  )  tion; Rights of Unit
                                       )  Holders -Certificates
                                       )

     (e)  Lapses or defaults with      )  *
          respect to periodic pay-     )
          ment plan certificates       )

     (f)  Voting rights as to Secu-    )  Rights of Unit Holders -
          rities under the Indenture   )  Certain Limitations;
                                       )  Amendment and Termination
                                       )  of the Indenture

     (g)  Notice to Holders as to      )
          change in:                   )

          (1)  Composition of assets   )  Administration of the
               of Trust                )  Trust - Reports to Unit
                                       )  Holders; The Trust - Sum-
                                       )  mary Description of the
                                       )  Portfolios
          (2)  Terms and Conditions    )  Amendment and Termination
               of Trust's Securities   )  of the Indenture
          (3)  Provisions of Inden-    )  Amendment and Termination
               ture                    )  of the Indenture

- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

          (4)  Identity of Depositor   )  Sponsor; Trustee
               and Trustee             )
                                       )
     (h)  Security Holders Consent     )
          required to change:

          (1)  Composition of assets   )  Amendment and Termination
               of Trust                )  of the Indenture
          (2)  Terms and conditions    )  Amendment and Termination
               of Trust's Securities   )  of the Indenture
          (3)  Provisions of Inden-    )  Amendment and Termination
               ture                    )  of the Indenture
          (4)  Identity of Depositor   )  *
               and Trustee             )

     (i)  Other principal features     )  Cover of Prospectus; Tax
          of the Trust's Securities    )  Status

11.  Type of securities comprising     )  The Trust - Summary De-
     units                             )  scription of the Portfo-
                                       )  lios; Objectives and Se-
                                       )  curities Selection; The
                                       )  Trust - Special Consid-
                                       )  erations

12.  Type of securities comprising     )  *
     periodic payment certificates     )

13.  (a)  Load, fees, expenses, etc.   )  Summary of Essential In-
                                       )  formation; Public Offer-
                                       )  ing of Units - Public Of-
                                       )  fering Price; - Profit of
                                       )  Sponsor;
                                       )  - Volume Discount; Ex-
                                       )  penses and Charges

     (b)  Certain information re-      )  *
          garding periodic payment     )
          certificates                 )





- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

     (c)  Certain percentages          )  Summary of Essential In-
                                       )  formation; Public Offer-
                                       )  ing of Units - Public Of-
                                       )  fering Price; - Profit of
                                       )  Sponsor; - Volume Dis-
                                       )  count

     (d)  Price differentials          )
                                       )  Public Offering Price
                                       )  - Public Offering of Units
                                       )

     (e)  Certain other loads, fees,   )  Rights of Unit Holders -
          expenses, etc. payable by    )  Certificates
          holders

     (f)  Certain profits receivable   )  Redemption - Purchase by
          by depositor, principal      )  the Sponsors of Units
          underwriters, trustee or     )  Tendered for Redemption
          affiliated persons           )

     (g)  Ratio of annual charges to   )  *
          income                       )

14.  Issuance of trust's securities    )  Introduction; Rights of
                                       )  Unit Holders - Certifi-
                                       )  cates

15.  Receipt and handling of pay-      )  Public Offering of Units
     ments from purchasers             )  - Profit of Sponsor
                                       )

16.  Acquisition and disposition of    )  Introduction; Amendment
     underlying securities             )  and Termination of the
                                       )  Indenture; Objectives and
                                       )  Securities Selection; The
                                       )  Trust - Summary Descrip-
                                       )  tion of the Portfolio;
                                       )  Sponsor - Responsibility
                                       )
                                       )




- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

17.  Withdrawal or redemption          )  Redemption; Public Offer-
                                       )  ing of Units - Secondary
                                       )  Market

18.  (a)  Receipt and disposition of   )  Administration of the
          income                       )  Trust; Reinvestment Pro-
                                       )  grams

     (b)  Reinvestment of distribu-    )  Reinvestment Programs
          tions                        )

     (c)  Reserves or special fund     )  Administration of the
                                       )  Trust - Distribution

     (d)  Schedule of distribution     )  *

19.  Records, accounts and report      )  Administration of the
                                       )  Trust - Records and Ac-
                                       )  counts; - Reports to Unit
                                       )  Holders

20.  Certain miscellaneous provi-      )  Amendment and Termination
     sions of the trust agreement      )  of the Indenture; Sponsor
                                       )  - Limitation on Liability
                                       )  - Resignation; Trustee
                                       )  - Limitation on Liability
                                       )  - Resignation

21.  Loans to security holders         )  *

22.  Limitations on liability of de-   )  Sponsor, Trustee; Evalua-
     positor, trustee, custodian,      )  tor - Limitation on Li-
     etc.                              )  ability

23.  Bonding arrangements              )  Included on Form
                                       )  N-8B-2

24.  Other material provisions of      )  *
     the trust agreement               )

     III.  ORGANIZATION PERSONNEL AND
          AFFILIATED PERSONS OF DEPOSITOR


- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

25.  Organization of Depositor         )  Sponsor

26.  Fees received by Depositor        )  Expenses and Charges -
                                       )  fees; Public Offering of
                                       )  Units - Profit of Sponsor
                                       )

27.  Business of Depositor             )  Sponsor and Included in
                                       )  Form N-8B-2

28.  Certain information as to offi-   )  Included in Form
     cials and affiliated persons of   )  N-8B-2
     Depositor                         )

29.  Voting securities of Depositor    )  Included in Form
                                       )  N-8B-2

30.  Persons controlling Depositor     )  *

31.  Compensation of Officers and      )  *
     Directors of Depositor            )

32.  Compensation of Directors of      )  *
     Depositor                         )

33.  Compensation of employees of      )  *
     Depositor                         )

34.  Remuneration of other persons     )  *
     for certain services rendered     )
     to trust                          )

     IV.  DISTRIBUTION AND REDEMPTION OF SECURITIES

35.  Distribution of trust's securi-   )  Public Offering of Units
     ties by states                    )  - Public Distribution

36.  Suspension of sales of trust's    )  *
     securities                        )

37.  Revocation of authority to dis-   )  *
     tribute                           )


- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

38.  (a)  Method of distribution       )  Public Offering of Units
     (b)  Underwriting agreements      )
     (c)  Selling agreements           )

39.  (a)  Organization of principal    )  Sponsor
          underwriter                  )
     (b)  N.A.S.D. membership of       )
          principal underwriter        )

40.  Certain fees received by prin-    )  Public Offering of Units
     cipal underwriter                 )  - Profit of Sponsor
                                       )

41.  (a)  Business of principal un-    )  Sponsor
          derwriter                    )

     (b)  Branch offices of princi-    )  *
          pal underwriter              )

     (c)  Salesman of principal un-    )  *
          derwriter                    )

42.  Ownership of trust's securities   )  *
     by certain persons                )

43.  Certain brokerage commissions     )  *
     received by principal under-      )
     writer                            )

44.  (a)  Method of valuation          )  Public Offering of Units
     (b)  Schedule as to offering      )  *
          price                        )
     (c)  Variation in offering        )  Public Offering of Units
          price to certain persons     )  - Volume Discount; Ex-
                                       )  change Option

45.  Suspension of redemption rights   )  *

46.  (a)  Redemption valuation         )  Public Offering of Units
                                       )  - Secondary Market; Re-
                                       )  demption

- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

     (b)  Schedule as to redemption    )  *
          price                        )

47.  Maintenance of position in un-    )  See items 10(d), 44 and
     derlying securities               )  46

     V.  INFORMATION CONCERNING THE TRUSTEE OR CUSTODIAN

48.  Organization and regulation of    )  Trustee
     Trustee                           )

49.  Fees and expenses of Trustee      )  Expenses and Charges

50.  Trustee's lien                    )  Expenses and Charges

     VI.  INFORMATION CONCERNING INSURANCE
          OF HOLDERS OF SECURITIES

51.  (a)  Name and address of Insur-   )  *
          ance Company                 )
     (b)  Type of policies             )  *
     (c)  Type of risks insured and    )  *
          excluded                     )
     (d)  Coverage of policies         )  *
     (e)  Beneficiaries of policies    )  *
     (f)  Terms and manner of can-     )  *
          cellation                    )
     (g)  Method of determining pre-   )  *
          miums                        )
     (h)  Amount of aggregate premi-   )  *
          ums paid                     )
     (i)  Persons receiving any part      *
          of premiums
     (j)  Other material provisions    )  *
          of the Trust relating to     )
          insurance                    )

     VII.  POLICY OF REGISTRANT

- -----------------------------

*    Inapplicable, answer negative or not required.
<PAGE>
Form N-8B-2                               Form S-6
Item Number                               Heading in Prospectus
- -----------                               ---------------------

52.  (a)  Method of selecting and      )  Introduction; Objectives
          eliminating securities       )  and Securities Selection;
          from the Trust               )  The Trust - Summary De-
                                       )  scription of the Portfo-
                                       )  lio; Sponsor - Responsi-
                                       )  bility
     (b)  Elimination of securities    )  *
          from the Trust               )
     (c)  Substitution and elimina-    )  Introduction; Objectives
          tion of securities from      )  and Securities Selection;
          the Trust                    )  Sponsor - Responsibility
     (d)  Description of any funda-    )  *
          mental policy of the Trust   )

53.  Taxable status of the Trust       )  Cover of Prospectus; Tax
                                       )  Status

     VIII.  FINANCIAL AND STATISTICAL INFORMATION

54.  Information regarding the         )  *
     Trust's past ten fiscal years     )

55.  Certain information regarding     )  *
     periodic payment plan certifi-    )
     cates                             )

56.  Certain information regarding     )  *
     periodic payment plan certifi-    )
     cates                             )

57.  Certain information regarding     )  *
     periodic payment plan certifi-    )
     cates                             )

58.  Certain information regarding     )  *
     periodic payment plan certifi-    )
     cates                             )

59.  Financial statements              )  Statement of Financial
     (Instruction 1(c) to Form S-6)    )  Condition



- -----------------------------

*    Inapplicable, answer negative or not required.

<PAGE>
INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
REGISTRATION STATEMENT RELATING TO UNITS OF THIS SERIES HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION BUT HAS NOT YET BECOME EFFECTIVE. SUCH UNITS
MAY NOT BE SOLD NOR MAY OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE
REGISTRATION STATEMENT BECOMES EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE
AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY
SALE OF THE UNITS IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOULD
BE UNLAWFUL PRIOR TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF
ANY SUCH STATE.
<PAGE>
   
                  SUBJECT TO COMPLETION DATED AUGUST 29, 1997
    
 
Parts A and B of this Prospectus do not contain all of the information with
respect to the investment company set forth in its registration statement and
exhibits relating thereto which have been filed with the Securities and Exchange
Commission, Washington, D.C. under the Securities Act of 1933 and the Investment
Company Act of 1940, and to which reference is hereby made.
 
[LOGO] DEAN WITTER SELECT EQUITY TRUST
 
MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO OCTOBER 1997
 ------------------------------------------------------------------------------
 
(A Unit Investment Trust)
 -----------------------------------------------------------------------------
 
   
The objective of the Trust is capital appreciation by an investment for
approximately 1 year in a fixed portfolio consisting of common stocks from
Morgan Stanley Dean Witter Global Equity Research's "Competitive Edge" - "Best
Ideas" as of [October   , 1997] (the "Competitive Edge - Best Ideas Stocks").
Such common stocks include both domestic and foreign equity securities issued by
companies in a variety of industries. The value of the Units of the Trust will
fluctuate with the value of the portfolio of underlying Securities. UNITS OF THE
TRUST ARE NOT DEPOSITS OR OBLIGATIONS OF, OR GUARANTEED OR ENDORSED BY, ANY
BANK, AND THE UNITS ARE NOT FEDERALLY INSURED BY THE FEDERAL DEPOSIT INSURANCE
CORPORATION, FEDERAL RESERVE BOARD OR ANY OTHER AGENCY. INVESTMENT IN UNITS OF
THE TRUST IS SUBJECT TO INVESTMENT RISK, INCLUDING THE POSSIBLE LOSS OF THE
PRINCIPAL AMOUNT INVESTED.
    
 
   
- --------------------------------------------------------------------------------
    
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.
 
- --------------------------------------------------------------------------------
 
   
<TABLE>
<CAPTION>
           SPONSOR                         TRUSTEE
- ------------------------------  ------------------------------
<S>                             <C>
  Dean Witter Reynolds Inc.                   [
     2 World Trade Center                     ]
   New York, New York 10048           New York, New York
</TABLE>
    
 
   
                        PROSPECTUS DATED OCTOBER  , 1997
    
<PAGE>
                        SUMMARY OF ESSENTIAL INFORMATION
 
                        DEAN WITTER SELECT EQUITY TRUST
   
        MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO
                                  OCTOBER 1997
    
 
   
                             AS OF          , 1997*
    
 
   
<TABLE>
<S>                                                                     <C>
Aggregate Value of Securities in Trust**..............................  $
Number of Units.......................................................             +
Fractional Undivided Interest in the Trust Represented by Each Unit...           1/th
Public Offering Price Per 100 Units:
    Aggregate Value of Securities in the Trust Divided by [    ] Units
     (times 100 Units)................................................  $
    Plus Sales Charge of 2.90% of Public Offering Price*** (2.925% of
     the amount invested in Securities)...............................
    Less Deferred Sales Charge per 100 Units..........................       (20.00)
                                                                        -----------
    Public Offering Price per 100 Units****...........................  $
                                                                        -----------
                                                                        -----------
Sponsor's Repurchase Price per 100 Units and Redemption Price per 100
  Units (based on the value of the underlying Securities, $    less
  than the Public Offering Price per 100 Units)*****..................  $
                                                                        -----------
                                                                        -----------
</TABLE>
    
 
   
<TABLE>
<S>                                                 <C>
Evaluation Time...................................  Close of the market: 4:00 P.M. New York time.
Record Dates......................................  1, 1997,     1, 1998,     1, 1998 and     1, 1998
Distribution Dates................................  15, 1997,       15, 1998,       15, 1998 and on or about
                                                          , 1998++
Minimum Principal Distribution....................  No distribution need be made from the Principal Account if
                                                    the balance therein is less than $1.00 per 100 Units
                                                    outstanding.
In-Kind Distribution Date.........................  , 1998
Liquidation Period................................  Not to exceed 14 business days after the In-kind
                                                    Distribution Date.++
Mandatory Termination Date........................  , 1998
Discretionary Liquidation Amount..................  The Indenture may be terminated by the Sponsor if the value
                                                    of the Trust at any time is less than 40% of the market
                                                    value of the Securities deposited in the Trust.+
Trustee's Fee (including estimated
expenses)******...................................  $  per 100 Units.
Organizational Expenses (estimated)+++............  $  per 100 Units.
Sponsor's Portfolio Supervision Fee...............  Maximum of $0.25 per 100 Units.
Deferred Sales Charge Payment Date................  The last business day of each month commencing           ,
                                                    1997.
Minimum Purchase: $1,000 ($250 for IRA's). The Sponsor offers a program which permits a lower minimum purchase
(see "Direct Invest").
</TABLE>
    
 
                                       i
<PAGE>
- ------------------------
 
   
    *The Initial Date of Deposit. The Indenture was signed and the initial
deposit of Securities with the Trustee was made on the Date of Deposit.
    
   
   **Based on the evaluation of the Securities as of 4:00 P.M. on          ,
1997.
    
   
  ***The sales charge consists of an Initial Sales Charge and a Deferred Sales
Charge. The Initial Sales Charge is computed by deducting the Deferred Sales
Charge ($20.00 per 100 Units) from the aggregate sales charge (a maximum of
2.90% of the Public Offering Price); thus on the date of this Summary of
Essential Information, the Initial Sales Charge is $  per 100 Units or   % of
the Public Offering Price. The Initial Sales Charge paid by a Unit Holder may be
more or less than $  per 100 Units because of the fluctuation of the value of
the Securities from that on the Initial Date of Deposit. The Initial Sales
Charge is reduced on a graduated basis on purchases of $25,000 or more (see
"Public Offering of Units--Volume Discount"). The Deferred Sales Charge is paid
through reduction of Trust assets by $2.00 per 100 Units on each Deferred Sales
Charge Payment Date through the sale of Securities on each such date or
distribution of cash available in the Principal Account for such payment. On a
repurchase, redemption or exchange of Units before the last Deferred Sales
Charge Payment Date, any remaining Deferred Sales Charge payments will be
deducted from the proceeds. Units purchased pursuant to the Reinvestment Program
are subject to that portion of the Deferred Sales Charge remaining at the time
of reinvestment (see "Reinvestment Program").
    
 ****This price is computed as of the Initial Date of Deposit and may vary from
such price on the date of this Prospectus or any subsequent date.
   
 *****This price is computed as of the Initial Date of Deposit and may vary from
such price on the date of this Prospectus or any subsequent date. This price
reflects deductions for remaining Deferred Sales Charge payments ($20.00 per 100
Units initially). In addition, after the initial offering period, the repurchase
and cash redemption prices will be further reduced to reflect the Trust's
estimated costs of liquidating Securities to meet the redemption, currently
estimated at $  per 100 Units.
    
   
******See: "Expenses and Charges" herein. The fee and the expenses accrue daily
and are payable on each Distribution Date. Estimated dividends from the
Securities, based on the last dividends actually paid, are expected by the
Sponsor to be sufficient to pay the estimated expenses of the Trust. In addition
to the Trustee's fee, brokerage costs borne by the Trust in connection with the
purchase of Securities by the Trustee with cash deposited in the Trust are
currently estimated at $  per 100 Units.
    
    +The number of Units will be increased as the Sponsor deposits additional
Securities into the Trust. See "Introduction", in Part B.
   ++The final distribution will be made within 5 business days following the
receipt of proceeds from the sale of all Portfolio Securities. (See:
"Administration of the Trust--Termination".)
   
  +++The cost of preparation and printing of the Indenture, Registration
Statement and other documents relating to the Trust, Federal and State
registration fees and costs, initial fees of the Trustee, and legal and auditing
expenses will be paid by the Trust and, therefore, will be borne by Unit
Holders. These organizational expenses will be amortized over the life of the
Trust. Organizational expenses per Unit have been estimated based on a Trust
with projected total assets of $[  ] million. To the extent the assets of the
Trust are less than such amount, the organizational expense per Unit will be
greater than the estimate shown.
    
 
                                       ii
<PAGE>
                 SUMMARY OF ESSENTIAL INFORMATION--(continued)
 
                                     FEE TABLE
 
THIS FEE TABLE IS INTENDED TO HELP YOU TO UNDERSTAND THE COSTS AND EXPENSES THAT
YOU WILL BEAR DIRECTLY OR INDIRECTLY. SEE PUBLIC OFFERING OF UNITS AND EXPENSES
AND CHARGES. ALTHOUGH THE TRUST HAS A TERM OF APPROXIMATELY ONE YEAR, AND IS A
UNIT INVESTMENT TRUST RATHER THAN A MUTUAL FUND, THIS INFORMATION IS PRESENTED
TO PERMIT A COMPARISON OF FEES (PERCENTAGES ARE BASED ON A $1,000 INVESTMENT IN
100 UNITS), ASSUMING THE PRINCIPAL AMOUNT AND DISTRIBUTIONS ARE EXCHANGED EACH
YEAR INTO A NEW TRUST SUBJECT ONLY TO THE DEFERRED SALES CHARGE AND TRUST
EXPENSES.
 
<TABLE>
<CAPTION>
                                                                                  AMOUNT PER
                                                                                    $1,000
                                                                                  INVESTMENT
UNIT HOLDER TRANSACTION EXPENSES                                                 IN 100 UNITS
- -----------------------------------------------------------------                -------------
<S>                                                                <C>           <C>
Initial Sales Charge Imposed on Purchase.........................  0.90%(a)      $     9.00
Deferred Sales Charge per Year...................................  2.00%(b)           20.00
                                                                   -----             ------
Maximum Sales Charge per Year....................................  2.90%         $    29.00
                                                                   -----             ------
                                                                   -----             ------
Maximum Sales Charge Imposed Per Year on Reinvested Dividends....                $    20.00(c)
</TABLE>
 
   
<TABLE>
<S>                                                                <C>           <C>
ESTIMATED ANNUAL TRUST OPERATING EXPENSES
 (AS A PERCENTAGE OF AVERAGE NET ASSETS)(D)
  Trustee's Fee..................................................      %         $
  Organizational Expenses (e)....................................      %
  Portfolio Supervision, Bookkeeping and Administrative Fees.....      %
  Other Operating Expenses.......................................    --                  --
                                                                   -----             ------
      Total......................................................      %         $
                                                                   -----             ------
                                                                   -----             ------
</TABLE>
    
 
                                      iii
<PAGE>
                             FEE TABLE--(continued)
 
                                      EXAMPLE
 
   
<TABLE>
<CAPTION>
                                                                  CUMULATIVE EXPENSES PAID FOR PERIOD
                                                              -------------------------------------------
                                                                            3           5          10
                                                              1 YEAR    YEARS(f)    YEARS(f)    YEARS(f)
                                                              -------   ---------   ---------   ---------
<S>                                                           <C>       <C>         <C>         <C>
An investor would pay the following expenses on a $1,000
 investment, assuming an estimated operating expense ratio
 of    % and a 5% annual return on the investment
 throughout the periods.....................................  $         $           $           $
 
The Example assumes reinvestment of all dividends and distributions and utilizes a 5% annual rate of
return as mandated by Securities and Exchange Commission regulations applicable to mutual funds. For
purposes of the Example, the Deferred Sales Charge imposed on reinvestment of dividends is not reflected
until the year following payment of the dividend; the cumulative expenses would be higher if sales
charges on reinvested dividends were reflected in the year of reinvestment. Because the reductions to the
repurchase and cash redemption prices described in footnote (*****) on page (ii) apply only to the
secondary market, these reductions have not been reflected in the figures above. The Example should not
be considered a representation of past or future expenses or annual rate of return; the actual expenses
and rate of return may be more or less than those assumed for purposes of the Example.
</TABLE>
    
 
                              -------------------
 
(a)  The Initial Sales Charge is actually the difference between 2.90% and the
     Deferred Sales Charge ($20.00 per 100 Units) and would exceed 0.90% if the
     Public Offering Price exceeds $1,000 per 100 Units.
 
(b)  The actual fee is $2.00 per month per 100 Units, irrespective of purchase
     or redemption price, paid on each Deferred Sales Charge Payment Date. If a
     Holder sells Units before all of these payments have been made, the balance
     of the Deferred Sales Charge will be paid from the sales proceeds. If the
     Unit purchase price exceeds $10 per Unit, the Deferred Sales Charge will be
     less than 2.00%; if the Unit purchase price is less than $10 per Unit, the
     Deferred Sales Charge will exceed 2.00%.
 
(c)  Reinvested dividends will be subject only to the Deferred Sales Charge
     remaining at the time of reinvestment which may be more or less than 2.00%
     of the Public Offering Price at the time of reinvestment (see "Reinvestment
     Program").
 
   
(d)  The estimates do not include the costs borne by the unit holders of
     purchasing and selling Securities.
    
 
   
(e)  The cost of preparation and printing of the Indenture, Registration
     Statement and other documents relating to the Trust, Federal and State
     registration fees and costs, initial fees of the Trustee, and legal and
     auditing expenses will be paid by the Trust and, therefore, will be borne
     by Unit Holders. Organizational expenses per Unit have been estimated based
     on a Trust with projected total assets of $[  ] million. To the extent the
     assets of the Trust are less than such amount, the organizational expense
     per Unit will be greater than the estimate shown.
    
 
   
(f) Although each Trust has a term of approximately one year and is a unit
    investment trust rather than a mutual fund, this information is presented to
    permit a comparison of fees and expenses, assuming the principal amount and
    distributions are exchanged each year into a new trust subject only to the
    Deferred Sales Charge.
    
 
                                       iv
<PAGE>
                 SUMMARY OF ESSENTIAL INFORMATION--(continued)
 
   
    THE TRUST--The Dean Witter Select Equity Trust, Morgan Stanley Dean Witter
Competitive Edge Best Ideas Portfolio October 1997 (the "Trust") is a unit
investment trust composed of publicly-traded common stocks or contracts to
purchase such stocks (the "Securities"). The objective of the Trust is capital
appreciation by an investment in the Competitive Edge - Best Ideas Stocks. The
Securities may appreciate or depreciate in value (or pay dividends) depending on
the full range of economic and market influences affecting corporate
profitability, the financial condition of issuers and the prices of equity
securities in general and the Securities in particular. Therefore, there is no
guarantee that the objective of the Trust will be achieved. Income is not an
objective of the Trust.
    
 
   
    On the Initial Date of Deposit and thereafter, the Sponsor may, under the
Indenture and Agreement, deposit additional Securities, contracts to purchase
additional Securities together with a letter of credit and/or cash (or a letter
of credit in lieu of cash) with instructions to purchase additional Securities
in order to create Additional Units while maintaining to the extent practicable
the proportionate relationship between the number of shares of each Security in
the Portfolio.
    
 
   
    SPECIAL CHARACTERISTICS OF THE TRUST--Morgan Stanley Dean Witter (MSDW)
Global Equity Research group is recognized as a world leader in global financial
research and provides comprehensive research and in-depth knowledge about
general markets and specific companies from around the world. Through its
on-going research and analysis, MSDW Global Equity Research has developed and
undertaken a comprehensive study which it calls Global Investing: The
Competitive Edge. It believes that companies with a sustainable competitive edge
in the operations of their business are worth more than their weaker
competitors, that these companies can be expected to earn higher incremental
returns on their businesses, and that these companies are less risky to own. The
Competitive Edge represents the list of those companies.
    
 
   
    Specifically, MSDW's equity research analysts and strategists evaluate
approximately 2,000 companies in 21 industry sectors worldwide. Of these, 238
companies were identified as having a competitive advantage in the global arena.
MSDW Global Equity Research has further identified a group of 84 companies in
which it believes that each of such company's competitive edge is not reflected
in its stock price. From this group, it then selects its "Best Ideas", a list of
approximately 40 companies which it considers to be the most attractive
investment opportunities of the group. Although not a fixed number, MSDW Global
Equity Research group will attempt to keep the number of Best Ideas stocks at
approximately 40 companies.
    
 
   
    Finally, the Sponsor has eliminated certain stocks due to market
capitalization and daily trading volume. The remaining securities constitute, on
an equally dollar-weighted basis, the portfolio of the Trust.
    
 
   
    The Securities represent most of the companies set forth in MSDW Global
Equity Research's Competitive Edge Best Ideas listing as of October  , 1997. In
contrast to the Trust Portfolio, the Competitive Edge Best Ideas listing is a
managed compilation. It is anticipated that this listing will be reviewed by
MSDW Global Equity Research approximately four times during a calendar year, at
which times the composition of such listing may change. The Trust Portfolio is
not managed. Therefore, regardless of any such list changes, the identity and
proportionate relationship of the Portfolio's Securities generally will remain
the same.
    
 
   
    Investors should note that the above criteria were applied to the Securities
selected for inclusion in the Trust Portfolio as of          , 1997. The
Securities were selected irrespective of any buy or sell recommendation by the
Sponsor although as of the selection date of the securities, such securities
were recommended by MSDW Global Equity Research, an affiliate of the Sponsor.
Subsequent to such date, the Securities may no longer meet the standard to
qualify for inclusion in the Competitive Edge - Best Ideas Stocks. However, the
Sponsor may, on and subsequent to the Initial Date of Deposit, deposit
additional Securities which reflect the Portfolio as of the Date of Deposit,
subject to permitted adjustments, and sell such additional Units created. The
sale of additional Units and the sale of Units in the secondary market may
continue even though the Securities would no longer be chosen for deposit into
the Trust if the selection process were to be made at such later time.
    
 
                                       v
<PAGE>
   
    RISK FACTORS--SPECIAL CONSIDERATIONS--An investment in Units of the Trust
should be made with an understanding of the risks inherent in an investment in
common stocks, including risks associated with the limited rights of holders of
common stock to receive payments from issuers of such stock; such rights are
inferior to those of creditors and holders of debt obligations or preferred
stock. Also, holders of common stock have the right to receive dividends only
when, as and if such dividends are declared by the issuer's board of directors.
The Securities comprising the portfolio of the Trust would generally continue to
be held by the Trust and may continue to be deposited notwithstanding their
removal from the Competitive Edge Best Ideas Stocks. Investors should also be
aware that the value of the underlying Securities in the Portfolio may fluctuate
in accordance with changes in the value of common stocks in general. Equity
markets have been at historically high levels and no assurance can be given that
these levels will continue. Although there are certain risks of price volatility
associated with investment in common stocks, your risk is reduced because your
capital is divided among stocks from several different industry groups.
    
 
   
    Although the Trust is a one year investment, the strategy is long-term.
Investors should consider reinvesting in successive trusts, for example, for at
least three to five years, to take advantage of the long-term strategy. There
can be no assurance, however, that the Sponsor will offer successive trusts.
Investors desiring to invest in successive trusts must so elect in connection
with the termination of the prior trust.
    
 
   
    In connection with the deposit by the Sponsor of cash (or a letter of credit
in lieu of cash) with instructions to purchase additional Securities in order to
create Additional Units, to the extent that the price of a Security fluctuates
between the time the cash is deposited and the time the cash is used to purchase
the Security, Units (including previously issued Units) may represent more or
less of that Security and more or less of other Securities in the Portfolio of
the Trust. In addition, the brokerage fees incurred in purchasing Securities
with such deposited cash will be borne by the Trust. Any Unit Holder who
purchased Units prior to the purchase of Securities with such deposited cash
would experience dilution as a result of any such brokerage fees.
    
 
   
    FOREIGN ISSUERS. The Portfolio may contain Securities of non-United States
issuers. Holding securities of non-United States companies may involve
investment risks that are different from those involved in holding securities of
domestic issues, including future political and economic developments, the
possible imposition of withholding taxes and exchange controls or other foreign
governmental restrictions which might adversely affect the payment of
distributions on Securities in the Portfolio. In addition, there may be less
publicly available information about a foreign issuer and foreign issuers may
not generally be subject to uniform accounting, auditing and financial reporting
standards, practices and requirements comparable to those applicable to domestic
issuers. Foreign securities markets, while growing in volume, have, for the most
part, substantially less volume than U.S. markets, and securities of many
foreign companies are less liquid and their prices more volatile than securities
of comparable domestic companies. Brokerage commissions and other transaction
costs on foreign securities exchanges are generally higher than in the United
States and there is generally less government supervision and regulation of
exchanges, brokers and issuers in foreign countries than there is in the United
States. Global and regional perceptions of foreign markets and currency exchange
rate fluctuations should also be considered since they may adversely affect the
value of the foreign securities.
    
 
   
    DISTRIBUTION--The Trustee will distribute any dividends (net of Trust
expenses) and any proceeds from the disposition of Securities not used for
redemption of Units received by the Trust on       15, 1997,       15, 1998,
      15, 1998 and on or about       , 1998 to holders of record on       1,
1997,       1, 1998,       1, 1998 and the Termination Date, respectively. Upon
termination of the Trust, the Trustee will distribute to each Unit Holder of
record its pro rata share of the Trust's assets, less expenses and less any
Deferred Sales Charge then payable or Unit Holders can elect to reinvest their
distributions automatically in units of a New Series (as defined below), if
offered by the Sponsor, which units acquired through reinvestment upon
termination will be subject only to a deferred sales charge (see "Administration
of the Trust--Termination"). The sale of Securities in the Trust during the
period prior to termination and upon termination may result in a lower amount
than might
    
 
                                       vi
<PAGE>
otherwise be realized if such sale were not required at such time due to
impending or actual termination of the Trust. For this reason, among others, the
amount realized by a Unit Holder upon termination may be less than the amount
paid by such Unit Holder. (See: "Administration of the Trust--Distribution".)
 
    The Sponsor anticipates that, based upon the last dividends actually paid by
the companies listed in the "Schedule of Portfolio Securities", dividends from
the Securities will be sufficient to (i) pay expenses of the Trust and (ii)
after such payment, to make distributions to Unit Holders as described herein.
(See: "Expenses and Charges" and "Administration of the Trust-- Distribution".)
 
   
    PUBLIC OFFERING PRICE--The Public Offering Price per 100 Units is computed
on the basis of the aggregate value of the underlying Securities next computed
after receipt of a purchase order plus cash on hand in the Trust, divided by the
number of Units outstanding times 100, plus a sales charge of 2.925% of such
evaluation per 100 Units (the amount invested in Securities); this results in a
sales charge of 2.90% of the Public Offering Price. A proportionate share of
amounts, if any, in the Income Account is also added to the Public Offering
Price. (See "Public Offering of Units--Public Offering Price".) The total sales
charge consists of an Initial Sales Charge and a Deferred Sales Charge, the
total of which equals 2.90% of the Public Offering Price or 2.925% of the amount
invested in Securities. The Initial Sales Charge is computed by deducting the
Deferred Sales Charge ($20.00 per 100 Units) from the aggregate sales charge;
thus, on the date of the Summary of Essential Information, the Initial Sales
Charge is $       per 100 Units or        % of the Public Offering Price. The
Initial Sales Charge paid by a Unit Holder may be more or less than $       per
100 Units because of the fluctuation of the value of the Securities from that on
the Initial Date of Deposit. The Initial Sales Charge will vary with changes in
the aggregate sales charge and is deducted from the purchase price of a Unit at
the time of purchase and paid to the Sponsor. The Initial Sales Charge will be
reduced on a graduated basis on purchases of $25,000 or more.
    
 
   
    In connection with future series, if any, Unit Holders acquiring Units
through an exchange or rollover of units of a previous series of the Dean Witter
Select Equity Trust will acquire such Units subject only to the Deferred Sales
Charge. The Deferred Sales Charge is paid through reduction of Trust assets by
$2.00 per 100 Units monthly on each Deferred Sales Charge Payment Date
commencing on the first Deferred Sales Charge Payment Date shown on the Summary
of Essential Information through the sale of Securities on each such date or
distribution of cash available for such payment. Units purchased pursuant to the
Reinvestment Program are subject only to deductions remaining of the Deferred
Sales Charge (see "Reinvestment Program"). If a Unit Holder exchanges, redeems
or sells his Units to the Sponsor prior to the last Deferred Sales Charge
Payment Date, the Unit Holder is obligated to pay any remaining Deferred Sales
Charge.
    
 
    MARKET FOR UNITS--The Sponsor, though not obligated to do so, intends to
maintain a market for the Units. If such market is not maintained, a Unit Holder
will be able to dispose of his Units through redemption at prices based on the
aggregate value of the underlying Securities. (See: "Redemption".) Market
conditions may cause such prices to be greater or less than the amount paid for
Units. The Sponsor's Repurchase Price, like the Redemption Price, will reflect
the deduction from the value of the underlying Securities of any unpaid amount
of the Deferred Sales Charge. Investors should note that the Deferred Sales
Charge of $2.00 per 100 Units will be deducted from Trust assets on the last
business day of each of the ten months commencing on the first Deferred Sales
Charge Payment Date shown on the Summary of Essential Information, and to the
extent the entire Deferred Sales Charge has not been so deducted or paid at the
time of repurchase or redemption of the Units, the remainder will be deducted
from the proceeds of sale or redemption or in calculating an in-kind redemption.
 
    TERMINATION--The Trust will terminate approximately 1 year after the Initial
Date of Deposit regardless of market conditions at that time. The Trust will
then liquidate. Unit Holders of 2,500 units or more may elect to receive shares
in-kind. Prior to termination of the Trust, the Trustee will begin to sell the
Securities held in the Trust over a period not to exceed 14 consecutive
 
                                      vii
<PAGE>
   
business days (the "Liquidation Period"). Monies held upon such sale of
Securities will be held uninvested in non-interest bearing accounts created by
the Indenture until distributed pro rata to Unit Holders on or about        ,
1998 and will be of benefit to the Trustee during such period. During the life
of the Trust, Securities will not be sold to take advantage of market
fluctuations.
    
 
   
    Because the Trust is not managed and the Securities can only be sold during
the Liquidation Period or under certain other limited circumstances described
herein, the proceeds received from the sale of Securities may be less than could
be obtained if the sale had taken place at a different time. Depending on the
volume of Securities sold and the prices of and demand for Securities at the
time of such sale, the sales of Securities from the Trust may tend to depress
the market prices of such Securities and hence the value of the Units, thus
reducing termination proceeds available to Unit Holders. In order to mitigate
potential adverse price consequences of heavy volume trading in the Securities
taking place over a short period of time and to provide an average market price
for the Securities, the Trustee will follow procedures set forth in the
Indenture to sell the Securities in an orderly fashion over a period not to
exceed the Liquidation Period. The Sponsor can give no assurance, however, that
such procedures will mitigate negative price consequences or provide a better
price for such Securities. The Trust may terminate earlier than on the Mandatory
Termination Date if the value of the Trust is less than the Discretionary
Liquidation Amount set forth under "Administration of the Trust--Termination."
    
 
   
    --PORTFOLIO CHARACTERISTICS. The Portfolio of the Trust consists of 40
issues of Securities, all of which are common stocks, issued by companies in the
categories set forth below:
    
 
   
<TABLE>
<CAPTION>
                                                                       PERCENTAGE OF
                                                    PORTFOLIO      AGGREGATE MARKET VALUE
CATEGORIES OF ISSUER                                 NUMBERS         OF TRUST PORTFOLIO
- -----------------------------------------------  ---------------  ------------------------
<S>                                              <C>              <C>
Integrated Petroleum...........................                                  %
Telecommunications.............................                                  %
Plastics, Fibers, Polymers.....................                                  %
Automotive.....................................                                  %
Photographic Equipment.........................                                  %
Paper, Packaging Products, Building
Materials......................................                                  %
Consumer, Chemical, Health Products............                                  %
Financial Services.............................                                  %
Food, Tobacco, Beverage........................                                  %
</TABLE>
    
 
   
    On the Date of Deposit, the aggregate market value of the Securities in the
Trust was $       .
    
 
   
    PERFORMANCE INFORMATION--Information on the performance of the Trust, one or
more Morgan Stanley Dean Witter Competitive Edge Best Ideas Portfolio series and
the Competitive Edge Best Ideas Stocks on the basis of changes in Unit price
(total return) may be included from time to time in advertisements, sales
literature and reports to current or prospective Unit Holders. Actual average
annualized returns may also be shown for consecutive series of the same Morgan
Stanley Dean Witter Competitive Edge Best Ideas Portfolio cycle. Information on
the performance of the Competitive Edge Best Ideas Stocks contained in this
Prospectus, as further updated, may also be included from time to time in such
material. Performance of individual Morgan Stanley Dean Witter Competitive Edge
Best Ideas Stocks Portfolios may also be shown along with performance of the
other Morgan Stanley Dean Witter Competitive Edge Best Ideas Stocks Portfolios
for comparable (though not necessarily identical) periods and on a combined
basis. Total return is computed by dividing share price changes plus dividends
reinvested at the end of each year by initial share prices, but does not reflect
commissions, taxes or Portfolio sales charges or expenses, which would decrease
the return. Actual average annualized return figures of a Portfolio would
reflect deduction of the maximum sales charge. Material reflecting annual
performance of a hypothetical investment in the Competitive Edge Best Ideas
Stocks may not reflect commissions, taxes, sales charges or expenses. No
provision is made for any income taxes payable. Past performance cannot
guarantee future results.
    
 
                                      viii
<PAGE>
                          INDEPENDENT AUDITORS' REPORT
 
THE UNIT HOLDERS, SPONSOR AND TRUSTEE
   
DEAN WITTER SELECT EQUITY TRUST
MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO OCTOBER 1997
    
 
   
    We have audited the accompanying statement of financial condition and
schedule of portfolio securities of the Dean Witter Select Equity Trust Morgan
Stanley Dean Witter Competitive Edge Best Ideas Portfolio October 1997 as of
           , 1997. These financial statements are the responsibility of the
Trustee. (See note (f) to the Statement of Financial Condition). Our
responsibility is to express an opinion on these financial statements based on
our audit.
    
 
   
    We conducted our audit in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. Our procedures included
confirmation of an irrevocable letter of credit and contracts for the purchase
of securities, as shown in the statement of financial condition and schedule of
portfolio securities as of            , 1997, by correspondence with
[           ], the Trustee. An audit also includes assessing the accounting
principles used and significant estimates made by the Trustee, as well as
evaluating the overall financial statement presentation. We believe that our
audit provides a reasonable basis for our opinion.
    
 
   
    In our opinion, the statement of financial condition and schedule of
portfolio securities referred to above present fairly, in all material respects,
the financial position of the Dean Witter Select Equity Trust Morgan Stanley
Dean Witter Competitive Edge Best Ideas Portfolio October 1997 as of
           , 1997 in conformity with generally accepted accounting principles.
    
 
   
DELOITTE & TOUCHE LLP
           , 1997
New York, New York
    
 
                                       ix
<PAGE>
                        STATEMENT OF FINANCIAL CONDITION
 
                        DEAN WITTER SELECT EQUITY TRUST
   
        MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO
                                  OCTOBER 1997
    
                 INITIAL DATE OF DEPOSIT,               , 1997
 
   
<TABLE>
<S>                                                           <C>
TRUST PROPERTY
    Sponsor's Contracts to purchase underlying Securities
     backed by an irrevocable letter of credit (a)..........  $
    Organizational costs (b)................................
                                                              -----------
      Total.................................................  $
                                                              -----------
                                                              -----------
LIABILITY AND INTEREST OF UNIT HOLDERS
    Liability--
      Payment of deferred portion of sales charge (c).......  $
      Accrued liability (b).................................
                                                              -----------
      Subtotal..............................................
                                                              -----------
    Interest of Unit Holders--
    Units of fractional undivided interest outstanding:
      Cost to investors (d).................................  $
      Gross underwriting commissions (e)....................
                                                              -----------
    Net amount applicable to investors......................  $
                                                              -----------
      Total.................................................  $
                                                              -----------
                                                              -----------
</TABLE>
    
 
                                       x
<PAGE>
- ------------------------
   
(a) The aggregate value of the Securities represented by Contracts to Purchase
    listed under "Schedule of Portfolio Securities" and their cost to the Trust
    are the same. The value is determined by the Trustee on the basis set forth
    under "Public Offering of Units--Public Offering Price" as of the Initial
    Date of Deposit. An irrevocable letter of credit drawn on [           ] York
    Branch in the amount of $  ,000.00 has been deposited with the Trustee.
    
 
   
(b) Organizational costs borne by the Trust have been deferred and will be
    amortized over the life of the Trust. Organizational costs have been
    estimated based on a Trust with projected total assets of $  million. To the
    extent the assets of the Trust are less than $  million, the organizational
    costs may be less although the per Unit amount may increase. To the extent
    the assets of the Trust are more, the organizational costs may be higher.
    
 
   
(c) Represents the aggregate amount of mandatory distributions of $2.00 per 100
    Units per month payable on the last business day of each month from
               , 1997 through            , 1998. Distributions will be made to
    an account maintained by the Trustee from which the Unit Holders' Deferred
    Sales Charge obligation to the Sponsor will be satisfied. If Units are
    redeemed prior to            , 1998, the remaining portion of the
    distribution applicable to such Units will be transferred to such account on
    the redemption date.
    
 
(d) The aggregate Public Offering Price is computed on the basis set forth under
    "Public Offering of Units--Public Offering Price" as of the evaluation time
    on the Date of Deposit.
 
(e) The aggregate sales charge of 2.90% of the Public Offering Price per 100
    Units is computed on the basis set forth under "Public Offering of
    Units--Public Offering Price".
 
(f)  The Trustee has custody of and responsibility for all accounting and
    financial books, records, financial statements and related data of the Trust
    and is responsible for establishing and maintaining a system of internal
    controls directly related to, and designed to provide reasonable assurance
    as to the integrity and reliability of, financial reporting of the Trust.
    The Trustee is also responsible for all estimates and accruals reflected in
    the Trust's financial statements. The Trustee determines the price for each
    underlying Security included in the Trust's Schedule of Portfolio Securities
    on the basis set forth in "Public Offering of Units--Public Offering Price".
    Under the Securities Act of 1933, as amended (the "Act"), the Sponsor is
    deemed to be an issuer of the Trust's Units. As such, the Sponsor has the
    responsibility of an issuer under the Act with respect to financial
    statements of the Trust included in the Registration Statement under the Act
    and amendments thereto.
 
                                       xi
<PAGE>
   
                        SCHEDULE OF PORTFOLIO SECURITIES
 
                        DEAN WITTER SELECT EQUITY TRUST
        MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE BEST IDEAS PORTFOLIO
                                  OCTOBER 1997
                   ON INITIAL DATE OF DEPOSIT,         , 1997
    
 
   
<TABLE>
<CAPTION>
                                                                PROPORTIONATE    PERCENTAGE
                                                                RELATIONSHIP    OF AGGREGATE    PRICE PER         COST OF
                                                    NUMBER OF    BETWEEN NO.    MARKET VALUE     SHARE TO       SECURITIES
   NO.      NAME OF ISSUER                           SHARES       OF SHARES       OF TRUST        TRUST       TO TRUST (1)(2)
- ---------   --------------------------------------  ---------   -------------   ------------   ------------   ---------------
<C>         <S>                                     <C>         <C>             <C>            <C>            <C>
</TABLE>
    
 
- ------------------------
   
(1) All Securities are represented entirely by contracts to purchase entered
    into on                         , 1997. Valuation of Securities by the
    Trustee was made on the basis of the closing sale price on the New York
    Stock Exchange on                         , 1997. The aggregate purchase
    price to the Sponsor for the Securities deposited in the Trust is
    $           .
    
 
   
(2) The Sponsor had no profit or loss on the Initial Date of Deposit.
    
 
    The Sponsor or affiliates thereof may have acted as an underwriter, manager
or co-manager of a public offering of the securities of the above issuers during
the last three years. Affiliates of the Sponsor may serve as specialists in the
Securities in this Trust on one or more stock exchanges and may have a long or
short position in any of these stocks or in options on any of these stocks, and
may be on the opposite side of public orders executed on the floor of an
exchange where the Securities are listed. An officer, director or employee of
the Sponsor may be an officer or director of one or more of the issuers of the
Securities in the Trust. The Sponsor may trade for its own account as an odd-lot
dealer, market maker, block positioner and/or arbitrageur in any of the
Securities or options relating thereto. The Sponsor, its affiliates, directors,
elected officers, employees and employee benefits programs may have either a
long or short position in any Security or option relating thereto.
 
                                      xii
<PAGE>
                                                               OFFERING FEATURES
 
   
DEAN WITTER SELECT EQUITY TRUST
MORGAN STANLEY DEAN WITTER COMPETITIVE EDGE
BEST IDEAS PORTFOLIO OCTOBER 1997
    
- ----------------------------------------------
   
    AN OPPORTUNITY TO INVEST FOR
    CAPITAL APPRECIATION POTENTIAL
    
- -------------------------------------------------------------
 
   
    - PORTFOLIO SELECTION -- Investment in the Competitive Edge Best Ideas
      Stocks (as of             , 1997) offers an opportunity for capital
      appreciation in the next year.
    
 
   
    - DIVERSIFICATION -- The Trust helps reduce risk because your investment is
      spread among common stocks from various industry groups. Individual
      investors would require a substantial capital commitment to achieve the
      level of diversification offered by the Trust without incurring odd-lot
      charges.
    
 
    - REINVESTMENT OPTION -- Investors may elect to have distributions
      automatically reinvested in additional units of the Trust subject to the
      then remaining deferred sales charge.
 
    - LOW MINIMUM INVESTMENT -- The Trust is priced at approximately $10 per
      unit and the minimum investment is $1,000 although investors may purchase
      any number of additional units they wish.
 
   
    - EASY LIQUIDITY -- The Sponsor intends to maintain a secondary market where
      Unit holders can sell units at the then-current market value based on net
      asset value (including deductions for any deferred sales charge then due).
    
 
   
    The Offering Features are a part of the prospectus and should be read in
                    conjunction with the entire prospectus.
    
<PAGE>
   
INVEST IN THE COMPETITIVE EDGE BEST IDEAS STOCKS
FOR AS LITTLE AS $1,000.
    
- ---------------------------------------------------------
THE SELECT EQUITY TRUSTS
 
       Achieving financial success in today's dynamic markets depends on
       selecting the right investment strategy. As new opportunities emerge,
       sparked by changing business trends, market strategies must be geared to
       capitalize on them. Because such opportunities may not be easily
       identified by individual investors, Dean Witter has developed the Select
       Equity Trusts which offer investors a simple and convenient way to
       participate in the equity market.
- --------------------------------------------------------------------------------
PORTFOLIO SELECTION
 
   
       The Morgan Stanley Dean Witter Competitive Edge Best Ideas portfolio
       consists of the common stocks selected by Morgan Stanley Dean Witter
       Global Equity Research analysts. The Trust is specifically designed for
       investors seeking capital appreciation. Because the Trust is a fixed
       portfolio of preselected securities, purchasers know in advance what they
       are investing in.
    
- --------------------------------------------------------------------------------
RISK FACTORS--SPECIAL CONSIDERATIONS
 
   
       The risks of an investment in Units of the Trust include price volatility
       resulting from factors affecting the common stock of the issuer of a
       portfolio security in particular and the domestic and foreign equity
       markets in general.
    
- --------------------------------------------------------------------------------
DIVERSIFICATION
 
   
       The Trust helps reduce risk because it allows Unit holders to participate
       in a more diversified portfolio of stocks in contrast to buying an
       individual stock. Although there are certain risks associated with
       investment in common stocks, the Trust helps reduce risk because an
       investment is divided among stocks from various industry groups. It would
       be difficult for the average investor to achieve a comparable level of
       diversification, without making a substantial capital commitment or
       incurring odd-lot charges.
    
- --------------------------------------------------------------------------------
REINVESTMENT OPTION
 
       Investors may elect to have distributions automatically reinvested in
       additional units of the Trust subject to the then remaining deferred
       sales charge.
- --------------------------------------------------------------------------------
NO TURNOVER
 
   
       The Morgan Stanley Dean Witter Competitive Edge Best Ideas portfolio is a
       portfolio of specific stocks. Listed within this prospectus are the
       stocks that make up the portfolio; under ordinary circumstances the
       issuers of the stocks in the portfolio will not change. Managed
       investment portfolios may have very high turnover rates over a one-year
       period. The Trust typically has no turnover during its life.
    
 
   
    The Offering Features are a part of the prospectus and should be read in
                    conjunction with the entire prospectus.
    
<PAGE>
- --------------------------------------------------
FLEXIBILITY THROUGH EXCHANGE PRIVILEGES
 
       Investors may elect, at any time, to exchange or rollover these units for
       units of another Dean Witter Select Trust at a sales charge less than the
       sales charge that a new investor would pay.
- --------------------------------------------------------------------------------
SHORT-TERM LIFE
 
       The Trust will terminate in approximately one year at which time the
       Portfolio will liquidate. Investors owning at least 2,500 units may elect
       to receive distributions in respect of their Units in kind. Investors not
       so electing will receive cash. Investors may, of course, sell or redeem
       Units prior to the Trust's termination.
- --------------------------------------------------------------------------------
EASY LIQUIDITY
 
       All or a portion of your Units may be liquidated at any time based on net
       asset value (including deduction for any deferred sales charge then
       payable). The price you receive will reflect market conditions and could
       be more or less than the price originally paid.
- --------------------------------------------------------------------------------
RETIREMENT ACCOUNTS
 
   
       This Trust may be an attractive investment vehicle for a self-directed
       IRA or self-directed self-employed retirement plan ("Keogh plan"). As a
       growth-oriented investment, it may be a suitable complement to help
       achieve overall portfolio diversification.
    
- --------------------------------------------------------------------------------
NO MARKET TIMING
 
   
       Due to the Trust's "buy and hold" strategy, an investor's money is
       generally invested at all times. Managed investment vehicles buy and sell
       securities and may have a sizable percentage of assets in cash.
    
 
   
    The Offering Features are a part of the prospectus and should be read in
                    conjunction with the entire prospectus.
    
<PAGE>
                               PROSPECTUS PART B
 
                        DEAN WITTER SELECT EQUITY TRUST
 
                                  INTRODUCTION
 
   
    This series of the Dean Witter Select Equity Trust (the "Trust") was created
under the laws of the State of New York pursuant to a Trust Indenture and
Agreement (the "Indenture") and a related Reference Trust Agreement (the
"Agreement") (collectively, the "Indenture and Agreement")*, between Dean Witter
Reynolds Inc. (the "Sponsor") and [                ] (the "Trustee"). The
Sponsor is a principal operating subsidiary of Morgan Stanley, Dean Witter,
Discover & Co., a publicly-held corporation. (See: "Sponsor".) The objective of
the Trust is capital appreciation through investment in a fixed portfolio of
Securities (the "Portfolio") of publicly-traded common stock. There is no
assurance that this objective will be met because the Securities may appreciate
or depreciate in value depending on the full range of economic and market
influences affecting corporate profitability, the financial condition of issuers
and the prices of equity securities in general and the Securities in particular.
Income is not an objective of the Trust.
    
 
   
    On the date of creation of the Trust (the "Initial Date of Deposit"), the
Sponsor deposited with the Trustee certain securities and contracts and funds
(represented by irrevocable letter(s) of credit issued by major commercial
bank(s)) for the purchase of such securities (collectively, the "Securities") at
prices equal to the market value of such Securities as determined by the Trustee
as of the Initial Date of Deposit and/or cash (or a letter of credit in lieu of
cash) with instructions to the Trustee to purchase such Securities. (See:
"Schedule of Portfolio Securities".) The Trust was created simultaneously with
the deposit of the Securities with the Trustee and the execution of the
Indenture and the Agreement. The Trustee then immediately recorded the Sponsor
as owner of the units (the "Units") comprising the entire ownership of the
Trust.
    
 
    Through this prospectus (the "Prospectus"), the Sponsor is offering the
Units, including Additional Units, as defined below, for sale to the public. The
holders of Units (the "Unit Holders") will have the right to have their Units
redeemed at a price based on the market value of the Securities (the "Redemption
Value") if they cannot be sold in the secondary market which the Sponsor,
although not obligated to, proposes to maintain. In addition, the Sponsor may
offer for sale, through this Prospectus, Units which the Sponsor may have
repurchased in the secondary market or upon the tender of such Units for
redemption. The Trustee has not participated in the selection of Securities for
the Trust, and neither the Sponsor nor the Trustee will be liable in any way for
any default, failure or defect in any Securities.
 
    With the deposit of the Securities in the Trust on the Initial Date of
Deposit, the Sponsor established a proportionate relationship between the number
of shares of each Security in the Portfolio. (The original proportionate
relationships on the Initial Date of Deposit are set forth in "Schedule of
Portfolio Securities".) The original proportionate relationships are subject to
adjustment under certain limited circumstances. (See: "Administration of the
Trust--Portfolio Supervision".) The Sponsor is permitted under the Indenture and
Agreement to deposit additional Securities, contracts to purchase additional
Securities together with a letter of credit and/or cash (or a letter of credit
in lieu of cash) with instructions to the Trustee to purchase additional
Securities in order to create additional Units ("Additional Units"). Any such
additional deposits made in the 90 day period following the creation of the
Trust will consist of securities identical to those already in the Trust and
will be in amounts which maintain, to the extent practicable, the original
proportionate relationship between the number of shares of each Security and any
cash in the Portfolio. It may not be possible to maintain the exact original
proportionate relationship because of price changes or other reasons.
 
- ------------------------
* Reference is hereby made to said Indenture and Agreement and any statements
  contained herein are qualified in their entirety by the provisions of said
  Indenture and Agreement.
<PAGE>
   
    Any cash deposited with instructions to purchase Securities may be held in
an interest bearing account by the Trustee. Any interest earned on such cash
will be the property of the Trust. Any cash deposited with instruction to
purchase Securities not used to purchase Securities and any interest not used to
pay Trust expenses will be distributed to Unit Holders on the earlier of the
first Distribution Date or 90 days after the Initial Date of Deposit. Additional
Units may be continuously offered for sale to the public by means of this
Prospectus. Subsequent to the 90 day period following the Initial Date of
Deposit any deposit of additional Securities and cash must exactly replicate the
portfolio immediately prior to such deposit.
    
 
   
    The Sponsor may acquire large volumes of additional Securities for deposit
into the Trust over a short period of time. Such acquisitions may tend to raise
the market prices of these Securities. To minimize the risk of price
fluctuations when purchasing Securities, the Trust may purchase Securities at
the closing price as of the Evaluation Time by entering into trades with
unaffiliated broker/dealers for the purchase of large quantities of shares. Such
trades will be entered into at an increased commission cost which will be borne
by the Trust. (See "Summary of Essential Information"). The Sponsor cannot
currently predict the actual market impact of the Sponsor's purchases of
additional Securities, because the actual volume of Securities to be purchased
and the supply and price of such Securities is not known.
    
 
    Units will be sold to investors at the Public Offering Price next computed
after receipt of the investor's order to purchase Units, if Units are available
to fill orders on the day that that price is set. If Units are not available or
are insufficient to fill the order, the investor's order will be rejected by the
Sponsor. The number of Units available may be insufficient to meet demand
because of the Sponsor's inability to or decision not to purchase and deposit
underlying Securities in amounts sufficient to maintain the proportionate
numbers of shares of each Security as required to create additional Units. The
Sponsor may, if unable to accept orders on any given day, offer to execute the
order as soon as sufficient Units can be created. An investor who agrees to this
will be deemed to place a new order for that number of Units each day until that
order is accepted. The investor's order will then be executed, when Units are
available, at the Public Offering Price next calculated after such continuing
order is accepted. The investor will, of course, be able to revoke his purchase
offer at any time prior to acceptance by the Sponsor. The Sponsor will execute
orders to purchase in the order it determines that they are received, i.e.,
orders received first will be filled first, except that indications of interest
prior to the effectiveness of the registration of the offering of Trust Units
which become orders upon effectiveness will be accepted according to the order
in which the indications of interest were received.
 
   
    On the Initial Date of Deposit, each Unit represented the fractional
undivided interest in the Securities and net income of the Trust set forth under
"Summary of Essential Information". Thereafter, if any Units are redeemed, the
amount of Securities in the Trust will be reduced, and the fractional undivided
interest represented by each remaining Unit in the balance of the Trust will be
increased. However, if Additional Units are issued by the Trust, the aggregate
value of the Securities in the Trust will be increased by amounts allocable to
such Additional Units and the fractional undivided interest in the balance will
be decreased. In connection with the deposit by the Sponsor of cash (or a letter
of credit in lieu of cash) with instructions to purchase additional Securities
in order to create Additional Units, to the extent that the price of a Security
fluctuates between the time the cash is deposited and the time the cash is used
to purchase the Security, Units (including previously issued Units) may
represent more or less of that Security and more or less of other Securities in
the Portfolio of the Trust. Units will remain outstanding until redeemed upon
tender to the Trustee by any Unit Holder (which may include the Sponsor) or
until the termination of the Trust pursuant to the Indenture and Agreement.
    
 
                                       2
<PAGE>
                                   THE TRUST
 
RISK FACTORS--SPECIAL CONSIDERATIONS
 
    An investment in Units of the Trust should be made with an understanding of
the risks which an investment in publicly-traded common stock may entail,
including the risk that the value of the Portfolio and hence of the Units will
decline with decreases in the market value of the Securities. The Trust will be
terminated and liquidated no later than the Mandatory Termination Date set forth
in the "Summary of Essential Information".
 
    On each Deferred Sales Charge Payment Date Securities will be sold pro rata
in an amount equal to $2.00 per 100 Units to pay the Deferred Sales Charge and
the proceeds will be distributed to the Sponsor. As Securities are sold to pay
the Deferred Sales Charge a Unit Holder's assets will be reduced and income per
Unit may be reduced.
 
SUMMARY DESCRIPTION OF THE PORTFOLIO
 
    As used herein, the term "Common Stocks" refers to the common stocks (or
contracts to purchase such common stocks) (any such contracts to purchase common
stocks to be accompanied by an irrevocable letter of credit sufficient to
perform such contracts), initially deposited in the Trust and described under
"Schedule of Portfolio Securities". The term "Securities" includes any
additional common stock or contracts to purchase additional common stock
together with the corresponding irrevocable letter of credit, subsequently
acquired by the Trust pursuant to the Indenture and Agreement.
 
   
    An investment in Units of the Trust should be made with an understanding
that the value of the underlying Securities, and therefore the value of Units,
will fluctuate, depending upon the full range of economic and market influences
which may affect the market value of such Securities. Certain risks are inherent
in an investment in equity securities, including the risk that the financial
condition of one or more of the issuers of the Securities may worsen or the
general condition of the common stock market may weaken. In such case, the value
of the Portfolio Securities and hence the value of Units may decline. Common
stocks are susceptible to general stock market movements and to volatile and
unpredictable increases and decreases in value as market confidence in and
perceptions of the issuers change from time to time. Such perceptions are based
upon varying reactions to such factors as expectations regarding domestic and
foreign economic, monetary and fiscal policies, inflation and interest rates,
currency exchange rates, economic expansion or contraction, and global or
regional political, economic or banking crises. The Sponsor cannot predict the
direction or scope of any of these factors. Additionally, equity markets have
been at historically high levels and no assurance can be given that these levels
will continue. THE TRUST HOLDS GROWTH STOCKS THAT MAY BE SUBJECT TO
ABOVE-AVERAGE PRICE VOLATILITY. THEREFORE THERE CAN BE NO ASSURANCE THAT THE
TRUST WILL BE EFFECTIVE IN ACHIEVING ITS OBJECTIVE OVER ITS ONE-YEAR LIFE OR
THAT FUTURE PORTFOLIOS SELECTED USING THE SAME METHODOLOGY AS THE TRUST DURING
CONSECUTIVE ONE-YEAR PERIODS WILL MEET THEIR OBJECTIVES. THE TRUST IS NOT
DESIGNED TO BE A COMPLETE EQUITY INVESTMENT PROGRAM.
    
 
   
    In addition, investors should understand that there are certain payment
risks involved in owning common stocks, including risks arising from the fact
that holders of common and preferred stocks have rights to receive payments from
the issuers of those stocks that are generally inferior to those of creditors
of, or holders of debt obligations issued by, such issuers. Furthermore, the
rights of holders of common stocks are inferior to the rights of holders of
preferred stocks. Holders of common stocks of the type held in the Portfolio
have a right to receive dividends only when, as and if, and in the amounts,
declared by the issuer's board of directors and to participate in amounts
available for distribution by the issuer only after all other claims on the
issuer have been paid or provided for. By contrast, holders of preferred stocks
have the right to receive dividends at a fixed rate when and as declared by the
issuer's board of directors, normally on a cumulative basis, but do not
ordinarily participate in other amounts available for distribution by the
issuing corporation. Cumulative preferred stock dividends must be paid before
common stock dividends, and any cumulative preferred stock dividend omitted is
added to future dividends payable to the holders of such cumulative preferred
stock. Preferred stocks are also entitled to rights on liquidation which are
senior to those of common stocks. For these reasons,
    
 
                                       3
<PAGE>
preferred stocks entail less risk than common stocks. However, neither preferred
nor common stocks represent an obligation or liability of the issuer and
therefore do not offer any assurance of income or provide the degree of
protection of capital of debt securities.
 
   
    The issuance of debt securities (as compared with both preferred and common
stock) and preferred stock (as compared with common stock) will create prior
claims for payment of principal and interest (in the case of debt securities)
and dividends and liquidation preferences (in the case of preferred stock) which
could adversely affect the ability and inclination of the issuer to declare or
pay dividends on its common stock or the rights of holders of common stock with
respect to assets of the issuer upon liquidation or bankruptcy. Further, unlike
debt securities which typically have a stated principal amount payable at
maturity (which value will be subject to market fluctuations prior thereto), or
preferred stocks which typically have a liquidation preference and which may
have stated optional or mandatory redemption provisions, common stocks have
neither a fixed principal amount nor a maturity date and have values which are
subject to market fluctuations for as long as the common stocks remain
outstanding. Additionally, market timing and volume trading will also affect the
underlying value of Securities, including the Sponsor's buying of additional
Securities and the Trust's selling of Securities during the Liquidation Period.
The value of the Securities in the Portfolio thus may be expected to fluctuate
over the entire life of the Trust to values higher or lower than those
prevailing on the Initial Date of Deposit. The Sponsor may direct the Trustee to
dispose of Securities under certain specified circumstances (see "Administration
of the Trust--Portfolio Supervision"). However, Securities will not be disposed
of solely as a result of normal fluctuations in market value.
    
 
   
    FOREIGN ISSUERS. Investment in securities of foreign issuers involves
investments risks that are different in some respects from an investment in a
trust that invests in securities of domestic issuers. Those investment risks
include future political and economic developments and the possible
establishment of exchange controls or other governmental restrictions which
might adversely affect the payment or receipt of payment of dividends on the
relevant Securities. In addition, for the foreign issuers that are not subject
to the reporting requirements of the Securities Exchange Act of 1934, there may
be less publicly available information than is available from a domestic issuer.
Also, foreign issuers are not necessarily subject to uniform accounting,
auditing and financial reporting standards, practices and requirements such as
those applicable to domestic issuers.
    
 
   
    Securities issued by non-U.S. issuers generally pay dividends in foreign
currencies, and are principally traded in foreign currencies. Therefore, there
is a risk that the United States dollar value of these Securities will vary with
fluctuations in the United States dollar foreign exchange rates for the relevant
currencies.
    
 
   
    FOREIGN EXCHANGE RATES. Securities that are principally traded in foreign
currencies involve investment risks that are substantially different from an
investment in securities that are principally traded in United States dollars.
This is because the United States dollar value of the foreign securities and of
the distributions from the Trust relating to the foreign securities will vary
with fluctuations in the United States dollar foreign exchange rates for the
relevant currencies. Most foreign currencies have fluctuated widely in value
against the United States dollar for many reasons, including supply and demand
of the respective currency, the soundness of the world economy and the strength
of the respective economy as compared to the economies of the United States and
other countries.
    
 
   
    The post-World War II international monetary system was, until 1973,
dominated by the Bretton Woods Treaty, which established a system of fixed
exchange rates and the convertibility of the United States dollar into gold
through foreign central banks. Starting in 1971, growing volatility in the
foreign exchange markets caused the United States to abandon gold convertibility
and to effect a small devaluation of the United States dollar. In 1973, the
system of fixed exchange rates between a number of the most important industrial
countries of the world, among them the United States and most Western European
countries, was completely abandoned. Subsequently, major industrialized
countries have adopted "floating" exchange rates, under which daily currency
valuations depend on supply and demand in a freely fluctuating international
market. Many smaller or developing countries have continued to "peg" their
currencies to the United States dollar although there has been some interest in
recent years
    
 
                                       4
<PAGE>
   
in "pegging" currencies to "baskets" of other currencies or to a Special Drawing
Right administered by the International Monetary Fund. In Europe a European
Currency Unit ("ECU") has been developed. Currencies are generally traded by
leading international commercial banks and institutional investors (including
corporate treasurers, money managers, pension funds and insurance companies).
From time to time, central banks in a number of countries also are major buyers
and sellers of foreign currencies, mostly for the purpose of preventing or
reducing substantial exchange rate fluctuations.
    
 
   
    Exchange rate fluctuations are partly dependent on a number of economic
factors including economic conditions within countries, the impact of actual and
proposed government policies on the value of the currencies, interest rate
differentials between the currencies, the balance of imports and exports of
goods and services and transfers of income and capital from one country to
another. These economic factors are influenced primarily by a particular
country's monetary and fiscal policies (although the perceived political
situation in a particular country may have an influence as well--particularly
with respect to transfers of capital). Investor psychology may also be an
important determinant of currency fluctuations in the short run. Moreover,
institutional investors trying to anticipate the future relative strength or
weakness of a particular currency may sometimes exercise considerable
speculative influence on currency exchange rates by purchasing or selling large
amounts of the same currency or currencies. However, over the long term, the
currency of a country with a low rate of inflation and a favorable balance of
trade should increase in value relative to the currency of a country with a high
rate of inflation and deficits in the balance of trade.
    
 
   
    The Trustee will estimate current exchange rates for the relevant currencies
based on activity in the various currency exchange markets. However, since these
markets are volatile, depending on the activity at any particular time of the
large international commercial banks, various central banks, large multinational
corporations, speculators and other buyers and sellers of foreign currencies,
and since actual foreign currency transactions may not be instantly reported,
the exchange rates estimated by the Trustee may not be indicative of the amount
in United States dollars the Trust would receive had the Trustee sold any
particular currency in the market.
    
 
   
    The foreign exchange transactions of a Trust may be concluded by the Trustee
with foreign exchange dealers acting as principals either on a spot (I.E., cash)
buying basis or on a forward foreign exchange basis on the date a Trust is
entitled to receive the applicable foreign currency. These forward foreign
exchange transactions will generally be of as short a duration as practicable
and will generally settle on the date of receipt of the applicable foreign
currency involving specific receivables or payables of the Trust accruing in
connection with the purchase and sale of its Securities and income received on
the Securities or the sale and redemption of Units. These transactions are
accomplished by contracting to purchase or sell a specific currency at a future
date and price set at the time of the contract. The cost to the Trust of
engaging in these foreign currency transactions varies with such factors as the
currency involved, the length of the contract period and the market conditions
then prevailing. Since transactions in foreign currency exchange are usually
conducted on a principal basis, fees or commissions are not normally involved.
Although foreign exchange dealers trade on a net basis, they do realize a profit
based upon the difference between the price at which they are willing to buy a
particular currency (bid price) and the price at which they are willing to sell
the currency (offering price). The relevant exchange rate used for evaluations
of the Securities may include the cost of buying or selling, as the case may be,
of any forward foreign exchange contract in the relevant currency.
    
 
   
    EXCHANGE CONTROLS. On the basis of the best information available to the
Sponsor at the present time none of the foreign securities is subject to
exchange control restrictions under existing law which would materially
interfere with payment to the Trust of amounts due on the foreign securities
either because the particular jurisdictions have not adopted any currency
regulations of this type or because the issues qualify for an exemption or the
Trust, as an extraterritorial investor, has qualified its purchase of the
foreign securities as exempt by following applicable "validation" or similar
regulatory or exemptive procedures. However, there can be no assurance that
exchange control regulations might not be adopted in the future which might
adversely affect payments to a Trust.
    
 
                                       5
<PAGE>
   
    In addition, the adoption of exchange control regulations and other legal
restrictions could have an adverse impact on the marketability of foreign
securities in the Portfolio and on the ability of the Trust to satisfy its
obligation to redeem Units tendered to the Trustee for redemption (see
"Redemption").
    
 
   
    LIQUIDITY. Foreign securities generally have not been registered under the
Securities Act of 1933 and may not be exempt from the registration requirements
of the Act. Sales of non-exempt Securities by a Trust in United States
securities markets are subject to severe restrictions and may not be
practicable. Accordingly, sales of these Securities by a Trust will generally be
effected only in foreign securities markets. Although the Sponsor does not
believe that a Trust will encounter obstacles in disposing of the Securities,
investors should realize that the Securities may be traded in foreign countries
where the securities markets are not as developed of efficient and may not be as
liquid as those in the United States. To the extent the liquidity of these
markets becomes impaired, however, the value of a Trust when responding to a
substantial volume of requests of redemption of Units (should redemptions be
necessary despite the market making activities of the Sponsor) received at or
about the same time could be adversely affected. This might occur, for example,
as a result of economic or political turmoil in a country in whose currency a
Trust had a substantial portion of its assets invested or should relations
between the United States and such foreign country deteriorate markedly.
    
 
   
    Even though the Securities are listed, the principal trading market for the
Securities may be in the over-the-counter market. As a result, the existence of
a liquid trading market for the Securities may depend on whether dealers will
make a market in the Securities. There can be no assurance that a market will be
made for any of the Securities, that any market for the Securities will be
maintained or of the liquidity of the Securities in any markets made. In
addition, the Trust may be restricted under the Investment Company Act of 1940
from selling Securities to the Sponsor. The price at which the Securities may be
sold to meet redemptions and the value of a Trust will be adversely affected if
trading markets for the Securities are limited or absent.
    
 
OBJECTIVE AND SECURITIES SELECTION
 
   
    The objective of the Trust is capital appreciation through an investment for
approximately one year in a fixed diversified portfolio of Securities chosen in
the manner described in the "Summary of Essential Information" in Part A herein.
There is, of course, no guarantee that the Trust's objective will be achieved.
Income is not an objective of the Trust.
    
 
    The Trust consists of such of the Securities listed under "Schedule of
Portfolio Securities" as may continue to be held from time to time in the Trust
and any additional Securities and/or contributed cash acquired and held by the
Trust pursuant to the provisions of the Indenture together with undistributed
income therefrom and undistributed cash realized from the disposition of
Securities (See: "Administration of the Trust"). Neither the Sponsor nor the
Trustee shall be liable in any way for any default, failure or defect in any of
the Securities. However, should any contract deposited hereunder fail and no
substitute Security be acquired, the Sponsor shall cause to be refunded the
sales charge relating to such security, plus the portion of the cost of the
failed contract listed under "Schedule of Portfolio Securities".
 
    Because certain Securities from time to time may be sold or their percentage
reduced under certain circumstances described herein, and because additional
Securities may be deposited into the Trust from time to time, the Trust is not
expected to retain for any length of time its present size and composition.
(See: "Administration of the Trust--Portfolio Supervision".)
 
    The Trust is organized as a unit investment trust and not as a management
investment company. Therefore, neither the Trustee nor the Sponsor has the
authority to manage the Trust's assets in an attempt to take advantage of
various market conditions to improve the Trust's net asset value, and further,
the Trust's Securities may be disposed of only under limited circumstances.
(See: "Administration of the Trust--Portfolio Supervision".)
 
    There is no assurance that any dividends will be declared or paid in the
future on the Securities initially deposited or to be deposited subsequently in
the Trust.
 
                                       6
<PAGE>
DISTRIBUTION
 
    The Record Dates and the Distribution Dates are set forth in Part A hereto.
(See: "Summary of Essential Information".) The distributions will be an amount
equal to such Unit Holder's pro rata portion of the amount of dividend income
received by the Trust and proceeds of the sale of Portfolio Securities,
including capital gains, not used for the redemption of Units, if any (less the
Trustee's fees, Sponsor's portfolio supervision fees and expenses).
Distributions for the account of beneficial owners of Units registered in
"street name" and held by the Sponsor will be made to the investment account of
such beneficial owners maintained with the Sponsor. Whenever required for
regulatory or tax purposes or if otherwise directed by the Sponsor, the Trustee
may make special distributions on special distribution dates to Unit Holders of
record on special record dates declared by the Trustee.
 
                            TAX STATUS OF THE TRUST
 
    In the opinion of Cahill Gordon & Reindel, special counsel for the Sponsor,
under existing Federal income tax law:
 
        The Trust is not an association taxable as a corporation for Federal
    income tax purposes, and income received by the Trust will be treated as
    income of the Unit Holders in the manner set forth below.
 
        Each Unit Holder will be considered the owner of a pro rata portion of
    each asset in the Trust under the grantor trust rules of Sections 671-678 of
    the Internal Revenue Code of 1986, as amended (the "Code"). The total tax
    cost of each Unit will equal the cost of Units (including the Initial Sales
    Charge) plus the amount of organizational expenses borne by the Unit Holder.
    A Unit Holder should determine the tax cost for each asset represented by
    the Holder's Units by allocating the total cost for such Units (including
    the Initial Sales Charge) among the assets in the Trust represented by the
    Units in proportion to the relative fair market values thereof on the date
    the Unit Holder purchases such Units. The proceeds received by a Unit Holder
    upon termination of the Trust or redemption of Units will be paid net of the
    Deferred Sales Charge. The relevant tax reporting forms sent to Unit Holders
    will also reflect the actual amounts paid to them, net of the Deferred Sales
    Charge. Accordingly, Unit Holders should not increase the total cost for
    their Units by the amount of the Deferred Sales Charge.
 
        A Unit Holder will be considered to have received all of the dividends
    paid on the Holder's pro rata portion of each Security when such dividends
    are received by the Trust including the portion of such dividend used to pay
    ongoing expenses and organizational expenses. In the case of a corporate
    Unit Holder, such dividends will qualify for the 70% dividends received
    deduction for corporations to the same extent as though the dividend paying
    stock were held directly by the corporate Unit Holder. An individual Unit
    Holder who itemizes deductions will be entitled to an itemized deduction for
    the Holder's pro rata share of fees and expenses paid by the Trust as though
    such fees and expenses were paid directly by the Unit Holder, but only to
    the extent that this amount together with the Unit Holder's other
    miscellaneous deductions exceeds 2% of the Holder's adjusted gross income. A
    corporate Unit Holder will not be subject to this 2% floor.
 
        Under the position taken by the Internal Revenue Service in Revenue
    Ruling 90-7, a distribution by the Trustee to a Unit Holder (or to the
    Holder's agent) of such Holder's PRO RATA share of the Securities in kind
    upon redemption or termination of the Trust will not be a taxable event to
    the Unit Holder. Such Unit Holder's basis for Securities so distributed will
    be equal to the Holder's basis for the same Securities (previously
    represented by the Holder's Units) prior to such distribution and the
    holding period for such Securities will be the shorter of the period during
    which the Unit Holder held the Units and the period for which the Securities
    were held in the Trust. A Unit Holder will have a taxable gain or loss,
    which will be a capital gain or loss except in the case of a dealer, when
    the Unit Holder disposes of such Securities in a taxable transfer.
 
        Under the income tax laws of the State and City of New York, the Trust
    is not an association taxable as a corporation and the income of the Trust
    will be treated as the income of the Unit Holders.
 
                                       7
<PAGE>
   
    In the case of dividends from foreign securities, U.S. Holders should
include as income their pro rata share of the amount of any foreign taxes
withheld with respect to such dividends. U.S. Holders should be entitled,
subject to applicable limitations, to either a credit or a deduction for foreign
taxes withheld with respect to such dividend payments.
    
 
   
    If the proceeds received by the Trust upon the sale or redemption of an
underlying Security exceed a Unit Holder's adjusted tax cost allocable to the
Security disposed of, that Unit Holder will realize a taxable gain to the extent
of such excess. Conversely, if the proceeds received by the Trust upon the sale
or redemption of an underlying Security are less than a Unit Holder's adjusted
tax cost allocable to the Security disposed of, that Unit Holder will realize a
loss for tax purposes to the extent of such difference except that upon
reinvestment of proceeds in a New Series the Internal Revenue Service may seek
to disallow such loss to the extent that the underlying securities in each trust
are substantially identical and the purchase of units of the New Series takes
place less than thirty-one days after the sale of the underlying Security. Under
the Code, capital gain of individuals, estates and trusts from assets held for
more than 1 year, but not more than 18 months, is subject to a maximum nominal
tax rate of 28%. Such net capital gain may, however, result in a disallowance of
itemized deductions and/or affect a personal exemption phase-out. The maximum
lower capital gain rate will be unavailable to those Unit Holders who have held
their units for less than a year and a day as of the Mandatory Termination Date
(or earlier termination of the Trust) or any day on which a Unit Holder's units
are exchanged or rolled over. The new 20% maximum capital gain provided by the
recently enacted Taxpayer Relief Act of 1997 will be unavailable to Unit Holders
with respect to capital gains derived from ownership of Units in the Trust.
    
 
    Each Unit Holder should consult his, her or its tax advisor with respect to
the application of the above general information to his, her or its own personal
situation.
 
                                RETIREMENT PLANS
 
    Units of the Trust may be suited for purchase by Individual Retirement
Accounts and pension plans or profit sharing and other qualified retirement
plans. Investors considering participation in any such plan should review
specific tax laws and pending legislation relating thereto and should consult
their attorneys or tax advisors with respect to the establishment and
maintenance of any such plan.
 
    A qualified retirement plan provides employee retirement benefits and is
funded by contributions from the employer (including contributions by a
self-employed individual, in which case the plan is sometimes called a Keogh
plan). The contributions are, within limits, deductible in determining the
taxable income of the contributing employer for Federal income tax purposes.
Income received by the plan is not taxed when received by it (nor are plan
losses deductible), but distributions from the plan are generally included in
ordinary income of the distributee upon receipt. A lump sum payout of the entire
amount held in such a plan can, however, be eligible for 5 or 10 year averaging.
 
    An individual retirement account (an "IRA") is similar to a qualified
retirement plan but contributions to an IRA up to $2,000 per year are generally
made by an individual from earned income, rather than by an employer.
(Additional contributions of up to $2,000 may also be made to an IRA of an
individual's spouse provided the combined income of the individual and his or
her spouse is sufficient.) An individual is permitted to contribute to an IRA
even though he or she is also covered by a qualified retirement plan; but, in
the case of higher-income individuals who are active participants in a qualified
retirement plan, IRA contributions are neither currently deductible nor taxed
when paid out by the IRA (although income earned in the IRA is taxed as ordinary
income when distributed). The IRA beneficiary must not have attained age 70 1/2
by the close of the taxable year for which an IRA contribution is made; and 5
and 10 year averaging is not allowable for IRA distributions.
 
    Distributions from qualified retirement plans must begin in minimum amounts
no later than the April 1 following the calendar year in which the employee
attains age 70 1/2 (or in the case of a person other than a 5% owner, April 1 of
the calendar year in which the employee retires, if later) or within 5 years
after his or her prior death if death occurs before distributions begin (with
later
 
                                       8
<PAGE>
distribution allowed for a surviving spouse and with lifetime annuity-type
payouts to any beneficiary permitted). Minimum required distributions from IRAs
are governed by similar rules (except that minimum distributions to the
individual for whom the IRA is maintained must in all cases begin no later than
the April 1 following the calendar year in which the individual attains age
70 1/2).
 
    Forms and arrangements for establishing qualified retirement plans and IRAs
are available from the Sponsor, as well as from other brokerage firms, other
financial institutions and others. Fees and charges with respect to such plans
and IRAs are not uniform and may vary from time to time as well as from
institution to institution.
 
    Distributions received from a qualified retirement plan or IRA before the
employee attains age 59 1/2 are subject to a 10% additional tax, unless the
distribution is (i) made on or after the employee's death, (ii) attributable to
his disablement, (iii) in the nature of a life annuity, (iv) made to the
employee after separation from service after attainment of age 55, or (v) made
for other reasons specified in the law. Qualifying distributions from a
qualified retirement plan or from an IRA may, however, be rolled over or
transferred to another qualified retirement plan or IRA under specified
circumstances.
 
    The foregoing information is of a general nature, does not purport to be
complete and relates only to the Federal income tax rules applicable to
qualified retirement plans and IRAs. State and local tax rules and foreign tax
regimes may treat qualified retirement plans and IRAs differently. Anyone
contemplating establishing a qualified retirement plan or IRA or investing funds
of such a plan or IRA in Trust units should consult his, her or its tax advisor
with respect to the tax consequences of any such action and the application of
the foregoing general tax information to his, her or its particular situation.
 
                            PUBLIC OFFERING OF UNITS
 
PUBLIC OFFERING PRICE
 
   
    The Public Offering Price of the Units is calculated on each business day
and is computed by adding to the aggregate market value of the Portfolio
Securities (as determined by the Trustee) next computed after receipt of a
purchase order, divided by the number of Units outstanding, the sales charge
shown in "Summary of Essential Information". Commissions and any other
transactional costs, if any, incurred by the Sponsor in connection with the
deposit of additional Securities or contracts to purchase additional Securities
for the creation of Additional Units will be added to the Public Offering Price.
After the Initial Date of Deposit, a proportionate share of amounts in the
Income Account and Principal Account and amounts receivable in respect of stocks
trading ex-dividend (other than money required to be distributed to Unit Holders
on a Distribution Date and money required to redeem tendered Units) is added to
the Public Offering Price. In the event a stock is trading ex-dividend at the
time of deposit of additional Securities, an amount equal to the dividend that
would be received if such stock were to receive a dividend will be added to the
Public Offering Price. The Public Offering Price per Unit is calculated to five
decimal places and rounded up or down to three decimal places. The Public
Offering Price on any particular date will vary from the Public Offering Price
on the Initial Date of Deposit (set forth in the "Summary of Essential
Information") in accordance with fluctuations in the aggregate market value of
the Securities, the amount of available cash on hand in the Trust and the amount
of certain accrued fees and expenses.
    
 
   
    As more fully described in the Indenture, the aggregate market value of the
Securities is determined by the Trustee based on closing prices on the day the
valuation is made as described under "Redemption--Computation of Redemption
Price" or, if there are no such reported prices, by taking into account the same
factors referred to under "Redemption--Computation of Redemption Price".
Determinations are effective for transactions effected subsequent to the last
preceding determination. The aggregate U.S. dollar market value of the foreign
Securities is determined on each business day by the Trustee based on closing
prices and relevant currency exchange rates on the day the valuation is made or,
if there are no such reported prices, by taking into account the same
    
 
                                       9
<PAGE>
   
factors referred to under "Redemption--Computation of Redemption Price", except
that the relevant exchange rate used for determining the value of Securities in
foreign currency may include the cost of any forward contract to purchase the
relevant currency.
    
 
    The sales charge consists of an Initial Sales Charge and a Deferred Sales
Charge. The Initial Sales Charge is computed by deducting the Deferred Sales
Charge ($20.00 per 100 Units) from the aggregate sales charge. The Initial Sales
Charge paid by a Unit Holder may be more or less than the Initial Sales Charge
on the Date of Deposit because of the fluctuation of the value of the Securities
from that on the Date of Deposit. The Deferred Sales Charge will initially be
$20.00 per 100 Units but will be reduced each month by one tenth; the Deferred
Sales Charge will be paid through monthly payments of $2.00 per 100 Units per
month commencing on the first Deferred Sales Charge Payment Date as shown on the
Summary of Essential Information through the sale of Securities on each such
date or distribution of cash available for such payment. To the extent the
entire Deferred Sales Charge has not been so paid at the time of repurchase,
redemption or exchange of the Units, any unpaid amount will be deducted from the
proceeds or in calculating an in kind distribution. For purchases of Units with
a value of $25,000 or more, the Initial Sales Charge is reduced on a graduated
basis as shown below under "Volume Discount". Units purchased pursuant to the
Reinvestment Program are subject only to any remaining Deferred Sales Charge
payments (see "Reinvestment Program"). Unit Holders investing the proceeds of
distribution from a previous terminating Series of Dean Witter Select Equity
Trust, upon purchase of Units of the Trust, will be subject only to the Deferred
Sales Charge on such Units. Unit Holders acquiring Units of the Trust pursuant
to an exchange of units of a different unit investment trust will not be charged
an initial sales charge at the time of the exchange but such Units acquired will
be subject to the Deferred Sales Charge.
 
PUBLIC DISTRIBUTION
 
    Units issued on the Initial Date of Deposit and Additional Units issued in
respect of additional deposits of Securities will be distributed to the public
by the Sponsor and through dealers at the Public Offering Price determined as
provided above. Unsold Units or Units acquired by the Sponsor in the secondary
market referred to below may be offered to the public by this Prospectus at the
then current Public Offering Price determined as provided above.
 
    The Sponsor intends to qualify Units in states selected by the Sponsor for
sale by the Sponsor and through dealers who are members of the National
Association of Securities Dealers, Inc. Sales to dealers during the initial
offering period will be made at prices which reflect a concession of 65% of the
applicable sales charge, subject to change from time to time. In addition, sales
of Units may be made pursuant to distribution arrangements with certain banks
and/or other entities subject to regulation by the Office of the Comptroller of
the Currency which are acting as agents for their customers. These banks and/or
entities are making Units of the Trust available to their customers on an agency
basis. A portion of the sales charge paid by these customers is retained by or
remitted to such banks or entities in an amount equal to the fee customarily
received by an agent for acting in such capacity in connection with the purchase
of Units. The Glass-Steagall Act prohibits banks from underwriting certain
securities, including Units of the Trust; however, this Act does permit certain
agency transactions, and banking regulators have not indicated that these
particular agency transactions are impermissible under this Act. In Texas, as
well as certain other states, any bank making Units available must be registered
as a broker-dealer in that State. The Sponsor reserves the right to reject, in
whole or in part, any order for the purchase of Units.
 
SECONDARY MARKET
 
    While not obligated to do so, it is the Sponsor's present intention to
maintain, at its expense, a secondary market for Units of this series of the
Dean Witter Select Equity Trust and to continuously offer to repurchase Units
from Unit Holders at the Sponsor's Repurchase Price. The Sponsor's Repurchase
Price is computed by adding to the aggregate value of the Securities in the
Trust, any cash on hand in the Trust including dividends receivable on stocks
trading ex-dividend (other than money required to redeem tendered Units and cash
deposited by the Sponsor to purchase Securities or cash held in the Reserve
Account) and deducting
 
                                       10
<PAGE>
therefrom expenses of the Trust, Sponsor, counsel and taxes, if any, any
remaining unpaid portion of the Deferred Sales Charge and cash held for
distribution to Unit Holders of record as of a date on or prior to the
evaluation; and then dividing the resulting sum by the number of Units
outstanding, as of the date of such computation. In addition, after the initial
offering period, the Sponsor's Repurchase Price will be reduced to reflect the
Trust's estimated costs of liquidating the Securities to meet redemption
requests. There is no sales charge incurred when a Unit Holder sells Units back
to the Sponsor other than the payment of the unpaid portion of the Deferred
Sales Charge. Any Units repurchased by the Sponsor at the Sponsor's Repurchase
Price may be reoffered to the public by the Sponsor at the then current Public
Offering Price. Any profit or loss resulting from the resale of such Units will
belong to the Sponsor.
 
    If the supply of Units exceeds demand (or for any other business reason),
the Sponsor may, at any time, occasionally, from time to time, or permanently,
discontinue the repurchase of Units of this series at the Sponsor's Repurchase
Price. In such event, although under no obligation to do so, the Sponsor may, as
a service to Unit Holders, offer to repurchase Units at the "Redemption Price".
Alternatively, Unit Holders may redeem their Units through the Trustee.
 
PROFIT OF SPONSOR
 
    The Sponsor receives a sales charge on Units sold to the public and to
dealers. The Sponsor may have also realized a profit (or sustained a loss) on
the deposit of the Securities in the Trust representing the difference between
the cost of the Securities to the Sponsor and the cost of the Securities to the
Trust (for a description of such profit (or loss) and the amount of such
difference on the initial Date of Deposit see: "Schedule of Portfolio
Securities"). The Sponsor may realize a similar profit (or loss) in connection
with each additional deposit of Securities. In addition, the Sponsor may have
acted as broker in transactions relating to the purchase of Securities for
deposit in the Trust. During the initial public offering period the Sponsor may
realize additional profit (or sustain a loss) due to daily fluctuations in the
prices of the Securities in the Trust and thus in the Public Offering Price of
Units received by the Sponsor. Cash, if any, received by the Sponsor from the
Unit Holders prior to the settlement date for purchase of Units or prior to the
payment for Securities upon their delivery may be used in the Sponsor's business
and may be of benefit to the Sponsor.
 
    The Sponsor may also realize profits (or sustain losses) while maintaining a
secondary market in the Units, in the amount of any difference between the
prices at which the Sponsor buys Units and the prices at which the Sponsor
resells such Units (such prices include a sales charge) or the prices at which
the Sponsor redeems such Units, as the case may be.
 
VOLUME DISCOUNT
 
    Although under no obligation to do so, the Sponsor intends to permit volume
purchasers of Units to purchase Units at a reduced sales charge. The Sponsor may
at any time change the amount by which the sales charge is reduced, or may
discontinue the discount altogether.
 
                                       11
<PAGE>
    The sales charge of 2.90% of the Public Offering Price will be reduced
pursuant to the following graduated scale for sales to any person of at least
$25,000 during the Initial Offering Period. The sales charge in the secondary
market, which will be reduced pursuant to the following graduated scale,
consists of an Initial Sales Charge and the remaining portions of the Deferred
Sales Charge. The following scale assumes a public offering price of $1,000.00
per 100 units:
 
<TABLE>
<CAPTION>
                                                           SALES CHARGE
                                          ----------------------------------------------
                                                                        PERCENT OF
                                                PERCENT OF          THE AMOUNT INVESTED
                                          PUBLIC OFFERING PRICE        IN SECURITIES
                                          ----------------------   ---------------------
<S>                                       <C>                      <C>
Less than $25,000.......................              2.90%                    2.926%
$25,000 to $49,999......................              2.75                     2.775
$50,000 to $99,999......................              2.50                     2.523
$100,000 to $249,999....................              2.25                     2.270
$250,000 to $999,999....................              2.00                     2.00
$1,000,000 or more......................              1.00                     1.00
</TABLE>
 
    The reduced sales charges as shown on the chart above will apply to all
purchases of Units of this Trust on any one day by the same person, partnership
or corporation (other than a dealer), in the amounts stated herein. For
purchases of $250,000.00 or more, the sales charge consists solely of a deferred
sales charge of $20.00 per 100 units for a purchase of $250,000.00 to
$999,999.99 and adjusted to total $10.00 per 100 units for a purchase of
$1,000,000.00 or more.
 
    Units held in the name of the purchaser's spouse or in the name of a
purchaser's child under the age 21 are deemed for the purposes hereof to be
registered in the name of the purchaser. The reduced sales charges are also
applicable to a trustee or other fiduciary, including a partnership or
corporation purchasing Units for a single trust estate or single fiduciary
account.
 
    The dealer concession will be 65% of the sales charge per Unit.
 
                                   REDEMPTION
 
RIGHT OF REDEMPTION
 
    One or more Units may be redeemed at the Redemption Price upon delivery of a
request for redemption to the Trustee at its unit investment trust office in the
City of New York, in form satisfactory to the Trustee. A Unit Holder may tender
its Units for redemption at any time after the settlement date for purchase. The
Redemption Price per Unit is calculated as set forth under "Computation of
Redemption Price". There is no sales charge incurred when a Unit Holder tenders
its Units to the Trustee for redemption other than the payment of any Deferred
Sales Charge then due.
 
    On the third business day following the tender to the Trustee of Units to be
redeemed the Unit Holder will be entitled to receive monies per Unit equal to
the Redemption Price per Unit as determined by the Trustee as of the Evaluation
Time on the date of tender.
 
    During the period in which the Sponsor maintains a secondary market for
Units, the Sponsor may repurchase any Unit presented for tender to the Trustee
for redemption no later than the close of business on the next Business Day
following such presentation.
 
    Units will be redeemed by the Trustee solely in cash for any one Unit Holder
tendering less than 2,500 Units. With respect to redemption requests regarding
at least 2,500 Units, the Sponsor may determine, in its discretion, to direct
the Trustee to redeem Units "in kind" by distributing Portfolio Securities to
the redeeming Unit Holder. The Sponsor may direct the Trustee to redeem Units
"in kind" even if it is then maintaining a secondary market in Units of the
Trust. Unit Holders redeeming "in kind" will receive an amount and value of
Trust Securities per Unit equal to the Redemption Price Per Unit as determined
as of the Evaluation Time
 
                                       12
<PAGE>
next following the tender as set forth herein under "Computation of Redemption
Price" below. The distribution "in kind" for redemption of Units will be held by
the Trustee for the account of, and for disposition in accordance with the
instructions of, the tendering Unit Holder. The tendering Unit Holder will be
entitled to receive whole shares of each of the underlying Portfolio Securities,
plus cash equal to the Unit Holder's pro rata share of the cash balance of the
Income and Principal Accounts and cash from the Principal Account equal to the
fractional shares to which such tendering Unit Holder is entitled. The Trustee,
in connection with implementing the redemption "in kind" procedures outlined
above, may make any adjustments necessary to reflect differences between the
Redemption Price of Units and the value of the Securities distributed "in kind"
as of the date of tender. If the Principal Account does not contain amounts
sufficient to cover the required cash distribution to the tendering Unit Holder,
the Trustee is empowered to sell Securities in the Trust Portfolio in the manner
discussed below. A Unit Holder receiving redemption distributions of Securities
"in kind" may incur brokerage costs and odd-lot charges in converting Securities
so received into cash. The Trustee will assess transfer charges to Unit Holders
taking Securities "in kind" according to its usual practice.
 
    The portion of the Redemption Price which represents the Unit Holder's
interest in the Income Account shall be withdrawn from the Income Account to the
extent available. The balance paid on any redemption, including dividends
receivable on stocks trading ex-dividend, if any, shall be drawn from the
Principal Account to the extent that funds are available for such purpose. The
Trustee is authorized by the Agreement to sell Securities in order to provide
funds for redemption. To the extent Securities are sold, the size and diversity
of the Trust will be reduced. Such sales may be required at a time when
Securities would not otherwise be sold and might result in lower prices than
might otherwise be realized. The Redemption Price received by a tendering Unit
Holder may be more or less than the purchase price originally paid by such Unit
Holder, depending on the value of the Securities in the Portfolio at the time of
redemption. Moreover, due to the minimum lot size in which Securities may be
required to be sold, the proceeds of such sales may exceed the amount necessary
for payment of Units redeemed. Such excess proceeds will be distributed pro rata
to all remaining Unit Holders of record on the next following Record Date.
 
    Securities to be sold for purposes of redeeming Units will be selected from
a list supplied by the Sponsor. If not so instructed by the Sponsor, the Trustee
will select the Securities to be sold so as to maintain, as closely as
practicable, the proportionate relationship between the number of shares of each
Security in the Trust.
 
COMPUTATION OF REDEMPTION PRICE
 
    The Trust Evaluation per Unit is determined as of the Evaluation Time stated
under "Summary of Essential Information" above (a) semiannually, on the last
Business Day of each of the months of June and December, (b) on the day on which
any Unit of the Trust is tendered for redemption (unless tender is made after
the Evaluation Time on such day, in which case Tender shall be deemed to have
been made on the next day subsequent thereto on which the New York Stock
Exchange is open for trading) and (c) on any other Business Day desired by the
Sponsor or the Trustee, (1) by adding:
 
        a.  The aggregate value of Securities in the Trust, as determined by the
    Trustee;
 
        b.  Cash on hand in the Trust, including dividends receivable on stocks
    trading ex-dividend, other than money deposited to purchase Securities or
    money credited to the Reserve Account;
 
        c.  All other assets of the Trust;
 
    (2) and then, by deducting from the resulting figure: amounts representing
any applicable taxes or governmental charges payable by the Trust for the
purpose of making an addition to the reserve account (as defined in the
Agreement, the "Reserve Account"), amounts representing estimated accrued fees
and expenses of the Trust (including legal and auditing expenses), amounts
representing unpaid fees of the Trustee, the Sponsor and counsel, any remaining
unpaid portion of the Deferred Sales Charge and monies held to redeem tendered
Units and for distribution to Unit Holders of record as of the Business Day
prior to the Evaluation being made on the days or dates set forth above and
then;
 
                                       13
<PAGE>
    (3) by dividing the result of the above computation by the total number of
Units outstanding on the date of such Evaluation. The resulting figure equals
the Redemption Price for each Unit.
 
    In addition, after the initial offering period, the Redemption Price will be
reduced to reflect the Trust's estimated costs of liquidating the Securities to
meet the redemption.
 
   
    The aggregate value of the Securities shall be determined by the Trustee in
good faith in the following manner: If the Securities are listed on one or more
national securities exchanges, such valuation shall be based on the closing
price on such exchange which is the principal market thereof and which shall be
deemed to be the New York Stock Exchange if the Securities are listed thereon
(unless the Trustee deems such price inappropriate as a basis for valuation). If
the Securities are not so listed, or, if so listed and the principal market
therefor is other than such exchange or there is no closing price on such
exchange, such valuation shall be based on the closing price in the
over-the-counter market (unless the Trustee deems such price inappropriate as a
basis for valuation) or if there is no such closing price, by any of the
following methods which the Trustee deems appropriate: (i) on the basis of
current bid prices of such Securities as obtained from investment dealers or
brokers (including the Depositor) who customarily deal in securities comparable
to those held by the Trust, or (ii) if bid prices are not available for any of
such Securities, on the basis of bid prices for comparable securities, or (iii)
by appraisal of the value of the Securities on the bid side of the market or by
such other appraisal as is deemed appropriate, or (iv) by any combination of the
above. The valuation of a foreign Security (in U.S. dollars based on the
applicable exchange rate) may take into consideration events or announcements
occurring after the close of the related foreign securities exchange and prior
to the Evaluation Time which could have a material effect on the value of a
Security. The relevant exchange rate used for evaluations of the Securities will
include the cost of any forward foreign exchange contract in the relevant
currency to correspond to the Trustee's settlement requirements for redemption
requests.
    
 
POSTPONEMENT OF REDEMPTION
 
    The right of redemption may be suspended and payment of the Redemption Price
per Unit postponed for more than seven calendar days following a tender of Units
for redemption (i) for any period during which the New York Stock Exchange, Inc.
is closed, other than for customary weekend and holiday closings, or (ii) for
any period during which, as determined by the Securities and Exchange
Commission, either trading on the New York Stock Exchange, Inc. is restricted or
an emergency exists as a result of which disposal or evaluation of the
Securities is not reasonably practicable, or (iii) for such other periods as the
Securities and Exchange Commission may by order permit. The Trustee is not
liable to any person or in any way for any loss or damage that may result from
any such suspension or postponement.
 
                                EXCHANGE OPTION
 
    Unit Holders of any Dean Witter Select Trust or any holders of units of any
other unit investment trust (collectively, "Holders") may elect to exchange any
or all of their units for units of one or more of any series of the Dean Witter
Select Equity Trust or for units of any other Dean Witter Select Trusts, that
may from time to time be made available for such exchange by the Sponsor (the
"Exchange Trusts"). Such an exchange is implemented by a sale of Units and a
purchase of the units of an Exchange Trust. Such units may be acquired at prices
based on reduced sales charges per unit. The purpose of such reduced sales
charge is to permit the Sponsor to pass on to the Holder who wishes to exchange
units the cost savings resulting from such exchange. The cost savings result
from reductions in time and expense related to advice, financial planning and
operational expense required for the Exchange Option. The following Exchange
Trusts are currently available: the Dean Witter Select Municipal Trust, the Dean
Witter Select Government Trust, the Dean Witter Select Equity Trust, the Dean
Witter Select Investment Trust and the Dean Witter Select Corporate Trust.
 
                                       14
<PAGE>
    Each Exchange Trust has different investment objectives: a Holder should
read the Prospectus for the applicable Exchange Trust carefully to determine the
investment objective prior to exercise of this option.
 
    This option will be available provided the Sponsor maintains a secondary
market in units of the applicable Exchange Trust and provided that units of the
applicable Exchange Trust are available for sale and are lawfully qualified for
sale in the state in which the Holder is a resident. While it is the Sponsor's
present intention to maintain a secondary market for the units of Exchange
Trusts, there is no obligation on its part to do so. Therefore, there is no
assurance that a market for units will in fact exist on any given date in which
a Holder wishes to sell or exchange Units; thus, there is no assurance that the
Exchange Option will be available to any Unit Holder. The Sponsor reserves the
right to modify, suspend or terminate this option. Sixty days notice will be
given prior to the date of the termination of or a material amendment to the
Exchange Option except that no notice need be given in certain circumstances
approved by the Securities and Exchange Commission. In the event the Exchange
Option is not available to a Unit Holder at the time such Unit Holder wishes to
exercise such option, the Unit Holder will be immediately notified and no action
will be taken with respect to such tendered Units without further instruction
from the Unit Holder.
 
    Exchanges will be affected in whole units only. Any excess proceeds from the
surrender of a Unit Holder's Units will be returned. Alternatively, Unit Holders
will be permitted to make up any difference between the amount representing the
Units being submitted for exchange and the amount representing the units being
acquired up to the next highest number of whole units.
 
    An exchange of Units pursuant to the Exchange Option will constitute a
"taxable event" under the Code, i.e., a Holder will recognize a gain or loss at
the time of exchange, except that, upon an exchange of Units for units of any
series of the Exchange Trusts which are grantor trusts for U.S. federal income
tax purposes the Internal Revenue Service may seek to disallow any loss incurred
upon such exchange to the extent that the underlying securities in each Trust
are substantially identical and the purchase of the units of an Exchange Trust
takes place less than thirty-one days after the sale of the Units. In order to
avoid the potential disallowance of losses for tax purposes, a Unit Holder may
notify the Sponsor that the Unit Holder desires to purchase units of the
Exchange Trust on the thirty-first day after the day of the sale of the Units
exchanged. The proceeds of the Units surrendered will be deposited in the Unit
Holder's brokerage account at the Sponsor and may be withdrawn at any time. Cash
from the account will be utilized to purchase units of the Exchange Trust on the
thirty-first day after the day of sale of the Units exchanged in accordance with
the procedures set forth above. A Unit Holder may revoke the order to purchase
at any time prior to the purchase on the thirty-first day by calling his
financial advisor. Units will be purchased at a price based upon the net asset
value per unit plus the applicable sales charge of 2.0%. However, there can be
no assurance that a market for units will exist on such date or that units will
be available for purchase on such date. If units are unavailable, the Sponsor
may acquire units in the secondary market or create units as soon as possible
thereafter, which units will be sold by the Sponsor based on the net asset value
on the date of purchase of the units plus the applicable sales charge of 2.0%.
The order does not create a contract or option to acquire units. If units are
not held in the Sponsor's inventory on the 31st day or if the Sponsor does not
create additional units or is unable to acquire units in the secondary market,
units of the Exchange Trust will not be purchased and the cash will remain in
the Unit Holder's account. A Unit Holder who exchanges Units of one Trust for
units of another Trust should consult his or her tax advisor regarding the
extent to which such exchange results in the recognition of a loss for Federal
and/or state or local income tax purposes.
 
    To exercise the Exchange Option, a Unit Holder should notify the Sponsor of
the desire to acquire units of one or more of the Exchange Trusts. Upon the
exchange of Units of the Trust, any Deferred Sales Charge balance will be
deducted from the exchange proceeds. If units of the applicable outstanding
series of the Exchange Trust are at that time available for sale, the Unit
Holder may select the series or group of series for which the Units are to be
exchanged. The Unit Holder will be provided with a current prospectus or
prospectuses relating to each series in which interest is indicated.
 
    The exchange transaction will operate in a manner essentially identical to
any secondary market transaction, i.e., Units will be repurchased at a price
based upon the aggregate bid side evaluation per Unit of the Securities in the
Portfolio. Units of the Exchange Trust will be sold to the Unit Holder at a
price equal to the net asset value based on the offering or bid side evaluation
(as
 
                                       15
<PAGE>
applicable) per unit of the securities in the Exchange Trust's Portfolio, plus
accrued interest, if any, and the applicable sales charge of 2.0% of the Public
Offering Price per Unit. If the Exchange Trust is a series of Dean Witter Select
Equity Trust, the applicable sales charge on such Trust will be the Deferred
Sales Charge of such Trust which may be more or less than 2.0% of the Public
Offering Price.
 
                                 DIRECT INVEST
 
   
    The Sponsor has established Dean Witter Direct InvestSM ("Direct Invest"),
an automatic investment program. Unit Holders may participate in Direct Invest
by completing the Direct Invest plan application. Pursuant to the program, a
Unit Holder may have any amount from $100 to $5,000 debited from a designated
bank account and transferred automatically, on a semi monthly, monthly or
quarterly basis, to The Bank of New York, Direct Invest servicing agent, for
investment in Units of the Trust. The Bank of New York will credit to the
account of each individual Unit Holder the number of Units (including fractional
Units) purchased. The Sponsor intends, although under no obligation, to offer a
new series of the Dean Witter Select Equity Trust, Morgan Stanley Dean Witter
Competitive Edge Best Ideas Portfolio every three month period. As each new
series is created, Units of each such new series will be automatically purchased
under the Direct Invest program subject to the applicable sales charge for such
series as disclosed in the prospectus for the series. A prospectus for each new
series will be sent to a Unit Holder participating in the program. The Unit
Holder is also eligible to elect to invest the distributions receivable from
units of a trust about to terminate in units of a subsequent series of the
Morgan Stanley The Competitive Edge Portfolio if and when offered at least three
weeks after the effective date of such Trust at the public offering price for
rollover investors on the close of business on such purchase date. See also
"Termination--The Rollover Option". Units of such New Series, the terms of which
will be substantially the same as the terms of the terminating trust, will be
subject only to the deferred sales charge. Distributions during the life of a
Trust with respect to Units purchased through Direct Invest (including Units
acquired through the rollover of such Units) will be automatically reinvested in
additional Units of such Trust (including fractional Units) subject only to any
remaining portions of the Deferred Sales Charge.
    
 
    Unit Holders, at any time, may terminate the automatic bank debit of the
Direct Invest program by so notifying The Bank of New York or their account
executive. The program may be terminated or changed by the Sponsor at any time
without notice. Unit Holders investing through an IRA or other pension plan may
be limited in the amount that may be invested in a trust in any one year. A tax
advisor should be consulted for the tax implications of participating in Direct
Invest and investing in Trusts, reinvesting distributions and investing proceeds
in a Subsequent Trust. (See: "Tax Status of the Trust"). Certain costs relating
to the Direct Invest program will be borne by the Trust and thus will be borne
indirectly by all Unit Holders.
 
                              REINVESTMENT PROGRAM
 
    Unit Holders may elect to have the distributions with respect to their Units
automatically reinvested in additional Units of the Trust subject only to any
remaining portions of the Deferred Sales Charge. (Reinvestment Units are not
subject to the Initial Sales Charge.) The Unit Holder may participate in the
Trust's reinvestment program (the "Program") by filing with the Trustee a
written notice of election. The Unit Holder's completed notice of election to
participate in the Program must be received by the Trustee at least ten days
prior to the Record Date applicable to any distribution in order for the Program
to be in effect as to such distribution. Elections may be modified or revoked on
similar notice.
 
    Such distributions, to the extent reinvested in the Trust, will be used by
the Trustee at the direction of the Sponsor in one or both of the following
manners. (i) The distributions may be used by the Trustee to purchase Units of
this Series of the Trust held in the Sponsor's inventory. The purchase price
payable by the Trustee for each of such Units will be equal to the applicable
Trust evaluation per Unit on (or as soon as possible after) the close of
business on the Distribution Date. The Units so purchased by the Trustee will be
issued or credited to the accounts of Unit Holders participating in the Program.
(ii) If there are no Units in the
 
                                       16
<PAGE>
Sponsor's inventory, the Sponsor may purchase additional Securities for deposit
into the Trust (as described in "Prospectus Part B--Introduction.") The
additional Securities with any necessary cash will be deposited by the Sponsor
with the Trustee in exchange for new Units. The distributions may then be used
by the Trustee to purchase the new Units from the Sponsor. The price for such
new Units will be the applicable Trust evaluation per Unit on (or as soon as
possible after) the close of business on the Distribution Date. (See "Public
Offering of Units--Public Offering Price.") The Units so purchased by the
Trustee will be issued or credited to the accounts of Unit Holders participating
in the Program. The Sponsor may terminate the Program if it does not have
sufficient Units in its inventory or it is no longer deemed practical to create
additional Units.
 
    No fractional Units will be issued under any circumstances. If, after the
maximum number of full Units has been issued or credited at the applicable
price, there remains a portion of the distribution which is not sufficient to
purchase a full Unit at such price, the Trustee will distribute such cash to
Unit Holders. The cost of administering the reinvestment program will be borne
by the Trust and thus will be borne indirectly by all Unit Holders.
 
                             RIGHTS OF UNIT HOLDERS
 
UNIT HOLDERS
 
    A Unit Holder is deemed to be a beneficiary of the Trust created by the
Indenture and Agreement and vested with all right, title and interest in the
Trust created therein. A Unit Holder may at any time tender its Units to the
Trustee for redemption.
 
    Unit Holders are required to hold their Units in uncertificated form. The
Trustee will credit a Unit Holder's account with the number of Units held by the
Unit Holder. Units are transferable only on the records of the Trustee upon
presentation of evidence satisfactory to the Trustee for each transfer and any
sums payable for taxes or other governmental charges imposed upon these
transactions and compliance with the formalities necessary to redeem Units.
 
CERTAIN LIMITATIONS
 
    The death or incapacity of any Unit Holder will not operate to terminate the
Trust nor entitle the legal representatives or heirs of such Unit Holder to
claim an accounting or to take any other action or proceeding in any court for a
partition or winding up of the Trust.
 
    No Unit Holder shall have the right to vote except with respect to removal
of the Trustee or amendment and termination of the Trust. (See: "Administration
of the Trust--Amendment" and "Administration of the Trust--Termination".) Unit
Holders shall have no right to control the operation or administration of the
Trust in any manner, except upon the vote of 51% of the Units outstanding at any
time for purposes of amendment, or termination of the Trust or discharge of the
Trustee, all as provided in the Agreement; however, no Unit Holder shall ever be
under any liability to any third party for any action taken by the Trustee or
Sponsor. Unit Holders will be unable to dispose of any of the Securities in the
Portfolio, as such, and will not be able to vote the Securities. The Trustee, as
holder of the Securities, will have the right to vote all of the voting
Securities held in the Trust, and will vote such Securities in accordance with
the instructions of the Sponsor, if given, otherwise the Trustee shall vote as
it, in its sole discretion, shall determine.
 
                              EXPENSES AND CHARGES
 
EXPENSES
 
   
    The estimated annual Trust expenses are listed in Part A--Summary of
Essential Information; if actual expenses exceed the estimated amounts such
excess will be borne by the Trust.
    
 
                                       17
<PAGE>
    All or a portion of the organizational expenses and charges incurred in
connection with the establishment of the Trust including the cost of the
preparation, printing and execution of the Indenture, Registration Statement and
other documents relating to the Trust, Federal and State registration fees and
costs, the initial fees and expenses of the Trustee and legal and auditing
expenses will be paid by the Trust and amortized over the life of the Trust.
Historically, the costs of establishing unit investment trusts have been borne
by a trust's sponsor. Advertising and selling expenses will be paid by the
Sponsor at no cost to the Trust.
 
FEES
 
    The Sponsor's fee, earned for portfolio supervisory services, is based upon
the largest number of Units outstanding during the computation period. The
Sponsor's fee as set forth in "Summary of Essential Information" may exceed the
actual costs of providing portfolio supervisory services for this Trust, but at
no time will the total amount the Sponsor receives for portfolio supervisory
services rendered to all series of the Dean Witter Select Equity Trust in any
calendar year exceed the aggregate cost to it of supplying such services in such
year.
 
    Under the Indenture and Agreement for its services as Trustee and evaluator,
the Trustee receives the fee set forth in "Summary of Essential Information".
Certain regular expenses of the Trust, including certain mailing and printing
expenses, are borne by the Trust.
 
    The Sponsor's fee, the Trustee's fees and the Trust expenses accrue daily
but are payable only on or before each Distribution Date from the Income
Account, to the extent funds are available and thereafter from the Principal
Account. Any of such fees may be increased without approval of the Unit Holders
in proportion to increases under the classification "All Services Less Rent" in
the Consumer Price Index published by the United States Department of Labor or,
if no longer published, a similar index. The Trustee, pursuant to normal banking
procedures, also receives benefits to the extent that it holds funds on deposit
in various non-interest bearing accounts created under the Indenture and
Agreement.
 
OTHER CHARGES
 
    The following additional charges are or may be incurred by the Trust as more
fully described in the Indenture and Agreement: (a) fees of the Trustee for
extraordinary services, (b) expenses of the Trustee (including legal and
auditing expenses) and of counsel designated by the Sponsor, (c) various
governmental charges, (d) expenses and costs of any action taken by the Trustee
to protect the Trust and the rights and interests of the Unit Holders, (e)
indemnification of the Trustee for any loss, liability or expenses incurred by
it in the administration of the Trust without gross negligence, bad faith,
wilful malfeasance or wilful misconduct on its part or reckless disregard of its
obligations and duties, (f) indemnification of the Sponsor for any losses,
liabilities and expenses incurred in acting as Sponsor or Depositor under the
Agreement without gross negligence, bad faith, wilful malfeasance or wilful
misconduct or reckless disregard of its obligations and duties, (g) expenditures
incurred in contacting Unit Holders upon termination of the Trust, and (h)
brokerage commissions or charges incurred in connection with the purchase or
sale of Securities.
 
PAYMENT
 
    The fees and expenses set forth herein are payable out of the Trust and when
so paid by or owing to the Trustee are secured by a lien on the Trust. Dividends
on the Securities are expected to be sufficient to pay the estimated expenses of
the Trust. If the balances in the Income and Principal Account are insufficient
to provide for amounts payable by the Trust, the Trustee has the power to sell
Securities to pay such amounts. To the extent Securities are sold, the size of
the Trust will be reduced and the proportions of the types of Securities may
change. Such sales might be required at a time when Securities would not
otherwise be sold and might result in lower prices than might otherwise be
realized. Moreover, due to the minimum lot size in which Securities may be
required to be sold, the proceeds of such sales may exceed the amount necessary
for the payment of such fees and expenses.
 
                                       18
<PAGE>
                          ADMINISTRATION OF THE TRUST
 
RECORDS AND ACCOUNTS
 
   
    The Trustee will keep records and accounts of all transactions of the Trust
at its unit investment trust office at [             ], New York, New York
10286. These records and accounts will be available for inspection by Unit
Holders at reasonable times during normal business hours. The Trustee will
additionally keep on file for inspection by Unit Holders an executed copy of the
Indenture and Agreement together with a current list of the Securities then held
in the Trust. In connection with the storage and handling of certain Securities
deposited in the Trust, the Trustee is authorized to use the services of
Depository Trust Company. These services would include safekeeping of the
Securities, coupon-clipping, computer book-entry transfer and institutional
delivery services. The Depository Trust Company is a limited purpose trust
company organized under the Banking Law of the State of New York, a member of
the Federal Reserve System and a clearing agency registered under the Securities
Exchange Act of 1934.
    
 
DISTRIBUTION
 
    Dividends payable to the Trust as a holder of record of its Securities are
credited by the Trustee to an Income Account, as of the date on which the Trust
is entitled to receive such dividends. Other receipts, including return of
investment and gain and amounts received upon the sale, pursuant to the
Indenture and Agreement, of rights to purchase other Securities distributed in
respect of the Securities in the Portfolio, are credited to a Principal Account.
Any distribution for each Unit Holder as of a Record Date will be made on the
next following Distribution Date or shortly thereafter and shall consist of an
amount approximately equal to the dividend income per Unit, after deducting
estimated expenses, if any, plus such Holder's pro rata share of the
distributable cash balance of the Principal Account. Proceeds received from the
disposition of any of the Securities which are not used for redemption of Units
will be held in the Principal Account to be distributed on the Distribution Date
following receipt of such proceeds. No distribution need be made from the
Principal Account if the balance therein is less than $1.00 per 100 Units
outstanding. A Reserve Account may be created by the Trustee by withdrawing from
the Income or Principal Accounts, from time to time, such amounts as it deems
requisite to establish a reserve for any taxes or other governmental charges
that may be payable out of the Trust. Funds held by the Trustee in the various
accounts created under the Indenture are non-interest bearing to Unit Holders.
 
    On each Deferred Sales Charge Payment Date Securities will be sold pro rata
in an amount equal to $2.00 per 100 Units to pay the Deferred Sales Charge and
the proceeds will be distributed to the Sponsor.
 
    The Trustee will follow a policy that it will place securities acquisition
or disposition transactions with a broker or dealer only if it expects to obtain
the most favorable prices and executions of orders. Transactions in securities
held in the Trust are generally made in brokerage transactions (as distinguished
from principal transactions) and the Sponsor may act as broker therein and
receive commissions thereon if the Trustee expects thereby to obtain favorable
prices and execution. The furnishing of statistical and research information to
the Trustee by any of the securities dealers through which transactions are
executed will not be considered in placing securities transactions.
 
PORTFOLIO SUPERVISION
 
    The original proportionate relationship between the number of shares of each
Security in the Trust will be adjusted to reflect the occurrence of a stock
dividend, a stock split, merger, reorganization or a similar event which affects
the capital structure of the issuer of a Security in the Trust but which does
not affect the Trust's percentage ownership of the common stock equity of such
issuer at the time of such event. If the Trust receives the securities of
another issuer as the result of a merger or reorganization of, or a spin-off,
split-off or split-up by the issuer of a Security included in the original
portfolio, the Trust may hold those securities as if they were one of the
Securities initially deposited and adjust the proportionate relationship
accordingly for all future subsequent
 
                                       19
<PAGE>
deposits. The Portfolio of the Trust is not "managed" by the Sponsor or the
Trustee; their activities described below are governed solely by the provisions
of the Indenture and Agreement. The Sponsor may direct the Trustee to dispose of
Securities upon failure of the issuer of a Security in the Trust to declare or
pay anticipated cash dividends, institution of certain materially adverse legal
proceedings, default under certain documents materially and adversely affecting
future declaration or payment of dividends, or the occurrence of other market or
credit factors that in the opinion of the Sponsor would make the retention of
such Securities in the Trust detrimental to the interests of the Unit Holders.
The Sponsor will direct the Trustee to sell Securities to pay portions of the
Deferred Sales Charge. Except as otherwise discussed herein, the acquisition of
any Securities for the Trust other than those initially deposited and deposited
in order to create additional Units, is prohibited. The Sponsor is authorized
under the Indenture to direct the Trustee to invest the proceeds of any sale of
Securities not required for the redemption of Units in eligible money market
instruments selected by the Sponsor which will include only negotiable
certificates of deposit or time deposits of domestic banks which are members of
the Federal Deposit Insurance Corporation and which have, together with their
branches or subsidiaries, more than $2 billion in total assets, except that
certificates of deposit or time deposits of smaller domestic banks may be held
provided the deposit does not exceed the insurance coverage on the instrument
(which currently is $100,000), and provided further that the Trust's aggregate
holding of certificates of deposit or time deposits issued by the Trustee may
not exceed the insurance coverage of such obligations and U.S. Treasury notes or
bills (which shall be held until the maturity thereof) each of which matures
prior to the earlier of the next following Distribution Date or 90 days after
receipt, the principal thereof and interest thereon (to the extent such interest
is not used to pay Trust expenses) to be distributed on the earlier of the 90th
day after receipt or the next following Distribution Date.
 
    During the life of the Trust, the Sponsor, as part of its administrative
responsibilities, shall conduct reviews to determine whether or not to recommend
the disposition of Securities. In addition, the Sponsor shall undertake to
perform such other reviews and procedures as it may deem necessary in order for
it to give the consents and directions, including directions as to voting on the
underlying Securities, required by the Indenture and Agreement. For the
administrative services performed in making such recommendations and giving such
consents and directions, and in making the reviews called for in connection
therewith the Sponsor shall receive the portfolio supervisory fee referred to
under "Summary of Essential Information".
 
VOTING OF THE PORTFOLIO SECURITIES
 
    Pursuant to the Indenture and Agreement, voting rights with respect to the
Portfolio Securities and Replacement Securities, if any, will be exercised by
the Trustee in accordance with the Indenture or the directions given by the
Sponsor.
 
REPORTS TO UNIT HOLDERS
 
    With each distribution, the Trustee will furnish to Unit Holders a statement
of the amount of income and other receipts distributed, including the proceeds
of the sale of the Securities (including the sale of any Securities to pay
portions of the Deferred Sales Charge), expressed in each case as a dollar
amount per Unit.
 
    Within a reasonable period of time after the last Business Day in each
calendar year, but not later than February 15, the Trustee will furnish to each
person who at any time during such calendar year was a Unit Holder of record a
statement setting forth:
 
        1.  As to the Income and Principal Account:
 
           (a) the amount of income received on the Securities;
 
           (b) the amount paid for redemption of Units;
 
           (c) the deductions for applicable taxes or other governmental
       charges, if any, and fees and expenses of the Sponsor, the Trustee and
       counsel;
 
                                       20
<PAGE>
           (d) the deductions of portions of the Deferred Sales Charge;
 
           (e) the amounts distributed from the Income Account;
 
           (f)  any other amount credited or deducted from the Income Account;
       and
 
           (g) the net amount remaining after such payments and deductions
       expressed both as a total dollar amount and as a dollar amount per Unit
       outstanding on the last business day of such calendar year.
 
        2.  The following information:
 
           (a) a list of the Securities as of the last business day of such
       calendar year;
 
           (b) the number of Units outstanding as of the last business day of
       such calendar year;
 
           (c) the Unit Value (as defined in the Agreement) based on the last
       Evaluation made during such calendar year; and
 
           (d) the amounts actually distributed during such calendar year from
       the Income and Principal Accounts, separately stated, expressed both as
       total dollar amounts and as dollar amounts per Unit outstanding on the
       Record Dates for such distributions.
 
AMENDMENT
 
    The Indenture and Agreement may be amended from time to time by the Trustee
and the Sponsor or their respective successors, without the consent of any of
the Unit Holders (a) to cure any ambiguity or to correct or supplement any
provision contained therein which may be defective or inconsistent with any
other provision contained therein; (b) to change any provision thereof as may be
required by the Securities and Exchange Commission or any successor governmental
agency exercising similar authority; or (c) to make such other provision in
regard to matters or questions arising thereunder as shall not adversely affect
the interest of the Unit Holders; provided, that the Indenture and Agreement may
also be amended from time to time by the parties thereto (or the performance of
any of the provisions of this Indenture and Agreement may be waived) with the
expressed written consent of Holders of Units evidencing 51% of the Units at the
time outstanding under the Indenture and Agreement for the purpose of adding any
provisions to or changing in any manner or eliminating any of the provisions of
the Indenture and Agreement or of modifying in any manner the rights of the Unit
Holders; provided, further however, that the Indenture and Agreement may not be
amended (nor may any provision thereof be waived) so as to (1) increase the
number of Units issuable in respect of the Trust above the aggregate number
specified in Part II of the Agreement or such lesser amount as may be
outstanding at any time during the term of the Indenture except as the result of
the deposit of Additional Securities, as therein provided, or reduce the
relative interest in the Trust of any Unit Holder without his consent, (2)
permit the deposit or acquisition thereunder of securities or other property
either in addition to or in substitution for any of the Securities except in the
manner permitted by the Trust Indenture as in effect on the date of the first
deposit of Securities or permit the Trustee to engage in business or investment
activities not specifically authorized in the Indenture and Agreement as
originally adopted or (3) adversely affect the characterization of the Trust as
a grantor trust for federal income tax purposes.
 
TERMINATION
 
    The Indenture and Agreement provides that the Trust will be liquidated
during the Liquidation Period as set forth under "Summary of Essential
Information" and terminated at the end of such period. Additionally, if the
value of the Trust as shown by any Evaluation is less than forty percent (40%)
of the value of the Securities deposited in the Trust on the Initial Date of
Deposit and thereafter, the Trustee will, if directed by the Sponsor in writing,
terminate the Trust. The Trust may also be terminated at any time by the written
consent of Unit Holders owning 51% or more of the Units then outstanding. Unit
Holders will receive their final
 
                                       21
<PAGE>
distributions (that is, their pro rata distributions realized from the sale of
Portfolio Securities plus any other Trust assets, less Trust expenses) according
to their Election Instructions. The Election Instructions will provide for the
following distribution options: (1) cash distributions; (2) distributions "in
kind" available only to any Unit Holder owning at least 2,500 Units; or (3)
investment of the distributions attributable to the Unit Holder in units of a
subsequent series of the Dean Witter Select Equity Trust as designated by the
Sponsor (the "New Series") if such New Series is offered at such time (the
"Rollover Option"). Unit Holders who do not tender properly completed Election
Instructions to the Trustee will be deemed to have elected a cash distribution.
 
    CASH OR "IN KIND" DISTRIBUTIONS. Unit Holders holding less than 2,500 Units
will receive distributions in respect of their Units at termination solely in
cash. Unit Holders holding at least 2,500 Units may indicate to the Trustee that
they wish to receive termination distributions "in kind", by returning to the
Trustee properly completed Election Instructions distributed by the Trustee to
such Unit Holders of record 45 days prior to the Termination Date. The Trustee
will duly honor such election instructions received on or before the In Kind
Distribution Date. Such Unit Holder will be entitled to receive whole shares of
each of the underlying Portfolio Securities and cash from the Principal Account
equal to the fractional shares to which such tendering Unit Holder is entitled.
A Unit Holder receiving distributions of Securities "in kind" may incur
brokerage and odd-lot costs in converting Securities so received into cash. The
Trustee will transfer the Securities to be delivered in kind to the account of,
and for disposition in accordance with the instructions of, the Unit Holder.
 
    THE ROLLOVER OPTION. A Unit Holder may elect to invest the distributions
attributable to the Unit Holder in units of a New Series subject only to the
deferred sales charge of the New Series. It is expected that the terms of the
New Series will be substantially the same as the terms of the Trust described in
this Prospectus, and that similar options to invest in a subsequent series of
the Trust will be exercisable as respects termination distributions from each
New Series of the Trust approximately one year after that New Series' creation.
The availability of this option does not constitute a solicitation of an offer
to purchase Units of a New Series or any other security. A Unit Holder's
election to exercise this option will be treated as an indication of interest
only. At any time prior to the purchase by a Unit Holder of units of a New
Series, such Unit Holder may change his investment strategy and receive, in
cash, the proceeds of the sale of the Securities.
 
    METHOD OF SECURITIES DISPOSAL. The Trustee will begin to sell the remaining
Securities held in the Trust on the next business day following the In-Kind
Date. Since the Trust is not managed, Securities in the Portfolio must be sold
in accordance with the Indenture, which provides for sales over a period of days
or on any one day during the Liquidation Period set forth in the "Summary of
Essential Information". Daily proceeds of such sales will be deposited into the
Trust, will be held in a non-interest bearing account until distributed and will
be of benefit to the Trustee. The sales of Portfolio Securities may tend to
depress the market prices for such Securities and thus reduce the proceeds
available to Unit Holders. The Sponsor believes that gradual liquidation of
Securities during the Liquidation Period may mitigate negative market price
consequences stemming from the trading of large volumes of Securities over a
short period of time. There can be no assurance, however, that such procedures
will effectively mitigate any adverse price consequences of heavy volume trading
or that such procedures will produce a better price for Unit Holders than might
have been obtained had all the Securities been sold on one particular day during
the Liquidation Period.
 
    The Trustee will, after deduction of brokerage charges and costs incurred in
connection with the sale of Securities, any fees and expenses of the Trust and
payment into the Reserve Account of any amount required for taxes or other
governmental charges that may be payable by the Trust, distribute to each Unit
Holder after due notice of such termination, such Unit Holder's pro rata share
in the Income and Principal Accounts. The sale of Securities in the Trust upon
termination may result in a lower amount than might otherwise be realized if
such sale were not required at such time. For this reason, among others, the
amount realized by a Unit Holder upon termination may be less than the amount
paid by such Unit Holder for Units.
 
                                       22
<PAGE>
                       RESIGNATION, REMOVAL AND LIABILITY
 
REGARDING THE TRUSTEE
 
    The Trustee shall be under no liability for any action taken in good faith
in reliance on prima facie properly executed documents or for the disposition of
monies or Securities in the Trust, nor shall the Trustee be liable or
responsible in any way for depreciation or loss incurred by reason of the
disposition of any Securities by the Trustee. However, the Trustee shall be
liable for wilful misfeasance, bad faith or gross negligence in the performance
of its duties or by reason of its reckless disregard of its obligations and
duties under the Indenture and Agreement. In the event of a failure of the
Sponsor to act, the Trustee may act under the Indenture and Agreement and shall
not be liable for any such action taken by it in good faith. The Trustee shall
not be personally liable for any taxes or other governmental charges imposed
upon the Trust or in respect of the Securities or the interest thereon. The
Agreement also contains other customary provisions limiting the liability of the
Trustee and providing for the indemnification of the Trustee for any loss or
claim accruing to it without gross negligence, bad faith, wilful misconduct,
wilful misfeasance or reckless disregard of its duties and obligations under the
Agreement on its part.
 
    The Trustee or any successor may resign by executing an instrument in
writing, filing the same with the Sponsor and mailing a copy of such notice of
resignation to all Unit Holders then of record. Upon receiving such notice the
Sponsor will use its best efforts to appoint a successor Trustee promptly. If
the Trustee becomes incapable of acting or becomes bankrupt or its affairs are
taken over by public authorities, or upon the determination of the Sponsor to
remove the Trustee for any reason, either with or without cause, the Sponsor may
remove the Trustee and appoint a successor as provided in the Agreement. If
within 30 days of the resignation of a Trustee no successor has been appointed
or, if appointed, has not accepted the appointment, the retiring Trustee may
apply to a court of competent jurisdiction for the appointment of a successor.
The resignation or removal of a Trustee becomes effective only when the
successor Trustee accepts its appointment as such or when a court of competent
jurisdiction appoints a successor Trustee.
 
REGARDING THE SPONSOR
 
    The Sponsor shall be under no liability to the Trust or to Unit Holders for
taking any action or for refraining from any action in good faith or for errors
in judgment. Nor shall the Sponsor be liable or responsible in any way for
depreciation or loss incurred by reason of the disposition of any Security. The
Sponsor will, however, be liable for its own wilful misfeasance, wilful
misconduct, bad faith, gross negligence or reckless disregard of its duties and
obligations under the Agreement.
 
    If at any time the Sponsor shall resign under the Agreement or shall fail or
be incapable of performing its duties thereunder or shall become bankrupt or its
affairs are taken over by public authorities, the Agreement directs the Trustee
to either (1) appoint a successor Sponsor or Sponsors at rates of compensation
deemed reasonable by the Trustee not exceeding amounts prescribed by the
Securities and Exchange Commission, or (2) terminate the Trust Indenture and
Agreement and the Trust and liquidate the Trust. The Trustee will promptly
notify Unit Holders of any such action.
 
                                 MISCELLANEOUS
 
SPONSOR
 
    Dean Witter Reynolds Inc. ("Dean Witter") is a corporation organized under
the laws of the State of Delaware and is a principal operating subsidiary of
Morgan Stanley, Dean Witter, Discover & Co. ("MSDWD"), a publicly-held
corporation. On May 31, 1997, Dean Witter, Discover & Co., Dean Witter's former
parent company, and Morgan Stanley Group Inc. merged to form MSDWD. Dean Witter
is a financial services company that provides to its individual, corporate, and
institutional clients services as a broker in securities and commodities, a
dealer in corporate, municipal, and government securities, an investment banker,
an investment
 
                                       23
<PAGE>
adviser, and an agent in the sale of life insurance and various other products
and services. Dean Witter is a member firm of the New York Stock Exchange, the
American Stock Exchange, the Chicago Board Options Exchange, other major
securities exchanges and the National Association of Securities Dealers, and is
a clearing member of the Chicago Board of Trade, the Chicago Mercantile
Exchange, the Commodity Exchange Inc., and other major commodities exchanges.
Dean Witter is currently servicing its clients through a network of more than
350 domestic and international offices with approximately 9,000 account
executives servicing individual and institutional client accounts.
 
TRUSTEE
 
   
    The Trustee is [                ]. The Trustee is organized under the laws
of the State of New York, is a member of the New York Clearing House Association
and is subject to supervision and examination by the Superintendent of Banks of
the State of New York, the Federal Deposit Insurance Corporation and the Board
of Governors of the Federal Reserve System. Unit Holders should direct inquiries
regarding distributions, address changes and other matters relating to the
administration of the Trust to the Trustee at Unit Investment Trust Division,
[                       ], New York, New York 10268-0974.
    
 
LEGAL OPINIONS
 
    The legality of the Units offered hereby has been passed upon by Cahill
Gordon & Reindel, a partnership including a professional corporation, 80 Pine
Street, New York, New York 10005, as special counsel for the Sponsor.
 
                                    AUDITORS
 
    The Statement of Financial Condition and Schedule of Portfolio Securities of
this series of the Dean Witter Select Equity Trust included in this Prospectus
have been audited by Deloitte & Touche LLP, certified public accountants, as
stated in their report as set forth in Part A of this Prospectus, and are
included in reliance upon such report given upon the authority of that firm as
experts in accounting and auditing.
 
                                       24
<PAGE>
  NO PERSON IS AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
  REPRESENTATIONS WITH RESPECT TO THIS INVESTMENT COMPANY NOT CONTAINED IN
  PARTS A AND B OF THIS PROSPECTUS; AND ANY INFORMATION OR REPRESENTATION NOT
  CONTAINED HEREIN MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED. PARTS A
  AND B OF THIS PROSPECTUS DO NOT CONSTITUTE AN OFFER TO SELL, OR A
  SOLICITATION OF AN OFFER TO BUY, SECURITIES IN ANY STATE TO ANY PERSON TO
  WHOM IT IS NOT LAWFUL TO MAKE SUCH OFFER IN SUCH STATE.
 
                               TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                        PAGE
                                                                        -----
<S>                                                                     <C>
PART A
Summary of Essential Information......................................      i
Independent Auditors' Report..........................................     ix
Statement of Financial Condition......................................      x
Schedule of Portfolio Securities......................................    xii
PART B
Introduction..........................................................      1
The Trust.............................................................      3
    Risk Factors--Special Considerations..............................      3
    Summary Description of the Portfolio..............................      3
    Objectives and Securities Selection...............................      6
    Distribution......................................................      7
Tax Status of the Trust...............................................      7
Retirement Plans......................................................      8
Public Offering of Units..............................................      9
    Public Offering Price.............................................      9
    Public Distribution...............................................     10
    Secondary Market..................................................     10
    Profit of Sponsor.................................................     11
    Volume Discount...................................................     11
Redemption............................................................     12
    Right of Redemption...............................................     12
    Computation of Redemption Price...................................     13
    Postponement of Redemption........................................     14
Exchange Option.......................................................     14
Direct Invest.........................................................     16
Reinvestment Program..................................................     16
Rights of Unit Holders................................................     17
    Unit Holders......................................................     17
    Certain Limitations...............................................     17
Expenses and Charges..................................................     17
    Expenses..........................................................     17
    Fees..............................................................     18
    Other Charges.....................................................     18
    Payment...........................................................     18
Administration of the Trust...........................................     19
    Records and Accounts..............................................     19
    Distribution......................................................     19
    Portfolio Supervision.............................................     19
    Voting of the Portfolio Securities................................     20
    Reports to Unit Holders...........................................     20
    Amendment.........................................................     21
    Termination.......................................................     21
Resignation, Removal and Liability....................................     23
    Regarding the Trustee.............................................     23
    Regarding the Sponsor.............................................     23
Miscellaneous.........................................................     23
    Sponsor...........................................................     23
    Trustee...........................................................     24
    Legal Opinions....................................................     24
Auditors..............................................................     24
</TABLE>
    
 
      37272
 
[LOGO] DEAN WITTER SELECT EQUITY TRUST
 
   
MORGAN STANLEY DEAN WITTER
COMPETITIVE EDGE BEST IDEAS
    
   
PORTFOLIO OCTOBER 1997
    
- --------------------------
(A Unit Investment Trust)
 
Sponsor:
- -------------------------------------------
[LOGO] DEAN WITTER REYNOLDS INC.
- -------------------------------------------
               Two World Trade Center - New York, New York 10048
 
             READ AND RETAIN THIS PROSPECTUS FOR FUTURE REFERENCE.
 
   
This prospectus may be used as a preliminary prospectus for a future series,
such as when Units of this Trust are no longer available, or for Investors who
will reinvest into subsequent series of the Trust. In such cases, Investors
should note that:
    
 
    Information contained herein is subject to amendment. A registration
statement relating to securities of a future series has been filed with the
Securities and Exchange Commission. These securities may not be sold nor may
offers to buy be accepted prior to the time the registration statement becomes
effective. This Prospectus shall not constitute an offer to sell or the
solicitation of an offer to buy nor shall there be any sale of these securities
in any State in which such offer, solicitation or sale would be unlawful prior
to registration or qualification under the securities laws of any such State.
<PAGE>


    PART II.  ADDITIONAL INFORMATION NOT REQUIRED IN PROSPECTUS


              CONTENTS OF REGISTRATION STATEMENT

       This registration statement on Form S-6 comprises the fol-
lowing documents:

       The facing sheet.

       The Cross Reference Sheet.

       The Prospectus.

       The signatures.


       Written consents of the following persons:

            -  Cahill Gordon & Reindel (included in Exhibit 5)

            -  Deloitte & Touche LLP

The following Exhibits:

  ***EX-3(i)     Certificate of Incorporation of Dean Witter
                 Reynolds Inc.

  ***EX-3(ii)    By-Laws of Dean Witter Reynolds Inc.

    *EX-4.1      Trust Indenture and Agreement, dated Sep-
                 tember 30, 1993.

   **EX-4.2      Draft of Reference Trust Agreement.

 ****EX-5        Opinion of counsel as to the legality of
                 the securities being registered.

 ****EX-23.1     Consent of Independent Auditors.

 ****EX-23.2     Consent of Cahill Gordon & Reindel
                 (included in Exhibit 5).

- ---------------------------

*     The Trust Indenture and Agreement is incorporated by refer-
      ence to exhibit of same designation filed with the Securities
      and Exchange Commission as an exhibit to the Registration
      Statement of Dean Witter Select Equity Trust, Selected Oppor-
      tunities Series 18, Registration number 33-50105.
**    Filed herewith.
***   Incorporated by reference to exhibit of same designation
      filed with the Securities and Exchange Commission as an ex-
      hibit to the Registration Statement of Sears Tax-Exempt In-
      vestment Trust, Insured Long Term Series 33 and Long Term Mu-
      nicipal Portfolio Series 106, Registration numbers 33-38086
      and 33-37629, respectively.
****  To be filed by amendment.
<PAGE>
                          SIGNATURES

          Pursuant to the requirements of the Securities Act of
1933, the registrant, Dean Witter Select Equity Trust, Morgan
Stanley Competitive Edge Best Ideas Portfolio October 1997, has 
duly caused this Registration Statement to be signed on its behalf
by the undersigned, thereunto duly authorized, all in the City
of New York and State of New York on the 28th day of August,
1997.

                              DEAN WITTER SELECT EQUITY TRUST,
                              MORGAN STANLEY COMPETITIVE EDGE
                              BEST IDEAS PORTFOLIO OCTOBER 1997
                              (Registrant)

                              By:  Dean Witter Reynolds Inc.
                                   (Depositor)



                                   Thomas Hines               
                                   -------------------------
                                   Thomas Hines
                                   -------------------------
                                   Authorized Signatory
<PAGE>
          Pursuant to the requirements of the Securities Act of
1933, this Registration Statement has been signed on behalf of
Dean Witter Reynolds Inc., the Depositor, by the following per-
son in the following capacities and by the following persons
who constitute a majority of the Depositor's Board of Directors
in the City of New York, and State of New York, on this 28th
day of August, 1997.

                              DEAN WITTER REYNOLDS INC.

Name                          Office
- -----                         ------

Philip J. Purcell             Chairman & Chief    )
                              Executive Officer   )
                              and Director***     )
Richard M. DeMartini          Director***
Robert J. Dwyer               Director***
Christine A. Edwards          Director***
Charles A. Fiumefreddo        Director**
James F. Higgins              Director***
Mitchell M. Merin             Director*
Stephen R. Miller             Director***
Richard F. Powers III         Director*
Philip J. Purcell             Director***
Thomas C. Schneider           Director**
William B. Smith              Director**

                              By:  Thomas Hines
                                   Thomas Hines
                                   Attorney-in-fact*, **, ***
- -----------------------------

*    Executed copies of the Powers of Attorney have been filed
     with the Securities and Exchange Commission in connection
     with Amendment No. 1 to the Registration Statement on Form
     S-6 for Dean Witter Select Equity Trust, Select 10 Indus-
     trial Portfolio 97-1, File No. 333-16839.

**   Executed copies of Powers of Attorney have been filed with
     the Securities and Exchange Commission in connection with
     Amendment No. 1 to the Registration Statement on Form S-6
     for Dean Witter Select Equity Trust, Select 10 Industrial
     Portfolio 96-4, File No. 333-10499.

***  Executed copies of Powers of Attorney have been filed with
     the Securities and Exchange Commission in connection with
     the Registration Statement on Form S-6 for Dean Witter Se-
     lect Equity Trust, Select 10 International Series 95-1,
     File No. 33-56389.
<PAGE>

                         Exhibit Index
                              To
                           Form S-6
                    Registration Statement
               Under the Securities Act of 1933


Exhibit No.         Document
- -----------         --------

     ***EX-3(i)     Certificate of Incorporation of Dean Witter
                    Reynolds Inc.

     ***EX-3(ii)    By-Laws of Dean Witter Reynolds Inc.

       *EX-4.1      Trust Indenture and Agreement, dated Sep-
                    tember 30, 1993.

      **EX-4.2      Draft of Reference Trust Agreement.

    ****EX-5        Opinion of counsel as to the legality of
                    the securities being registered.

    ****EX-23.1     Consent of Independent Auditors.

    ****EX-23.2     Consent of Cahill Gordon & Reindel
                    (included in Exhibit 5).


- -----------------------------

*    The Trust Indenture and Agreement is incorporated by ref-
     erence to exhibit of same designation filed with the Secu-
     rities and Exchange Commission as an exhibit to the Regis-
     tration Statement of Dean Witter Select Equity Trust, Se-
     lected Opportunities Series 18, Registration number 33-
     50105.

**   Filed herewith.

***  Incorporated by reference to exhibit of same designation
     filed with the Securities and Exchange Commission as an
     exhibit to the Registration Statement of Sears Tax-Exempt
     Investment Trust, Insured Long Term Series 33 and Long
     Term Municipal Portfolio Series 106, Registration numbers
     33-38086 and 33-37629, respectively.

**** To be filed by amendment.


<PAGE>

                                                     Exhibit 4.2


                DEAN WITTER SELECT EQUITY TRUST
    MORGAN STANLEY COMPETITIVE EDGE BEST IDEAS OCTOBER 1997

          This Reference Trust Agreement dated           , 1997
between DEAN WITTER REYNOLDS INC., as Depositor, and The Bank
of New York, as Trustee, sets forth certain provisions in full
and incorporates other provisions by reference to the document
entitled "Dean Witter Select Equity Trust, Trust Indenture and
Agreement" (the "Basic Agreement") dated September 30, 1993.
Such provisions as are incorporated by reference constitute a
single instrument (the "Indenture").

                       WITNESSETH THAT:

          In consideration of the premises and of the mutual
agreements herein contained, the Depositor and the Trustee
agree as follows:

                              I.

            STANDARD TERMS AND CONDITIONS OF TRUST

          Subject to the provisions of Part II hereof, all the
provisions contained in the Basic Agreement are herein incorpo-
rated by reference in their entirety and shall be deemed to be
a part of this instrument as fully and to the same extent as
though said provisions had been set forth in full in this in-
strument except that the Basic Agreement is hereby amended as
follows:

          A.   The first sentence of Section 2.01 is amended to
     add the following language at the end of such sentence:
     "and/or cash (or a letter of credit in lieu of cash) with
     instructions to the Trustee to purchase one or more of
     such Securities which cash (or cash in an amount equal to
     the face amount of the letter of credit), to the extent
     not used by the Trustee to purchase such Securities within
     the 90-day period following the first deposit of Securi-
     ties in the Trust, shall be distributed to Unit Holders on
     the Distribution Date next following such 90-day period or
     such earlier date as the Depositor and the Trustee deter-
     mine".

          B.   The first sentence of Section 2.06 is amended to
     add the following language after "Securities"))": "and/or
     cash (or a letter of credit in lieu of cash) with instruc-
     tions to the Trustee to purchase one or more Additional
<PAGE>





                              -2-


     Securities which cash (or cash in an amount equal to the
     face amount of the letter of credit), to the extent  not
     used by the Trustee to purchase such Additional Securities
     within the 90-day period following the first deposit of
     Securities in the Trust, shall be distributed to Unit
     Holders on the Distribution Date next following such 90-
     day period or such earlier date as the Depositor and the
     Trustee determine".

          C.   Article III, entitled "Administration of Trust",
     Section 3.01 Initial Cost shall be amended as follows:

               (i)  the first part of the first sentence of
          Section 3.01 Initial Cost shall be amended to substi-
          tute the following language before the phrase
          "PROVIDED, HOWEVER":

                    "With respect to the Trust, the cost of the
               preparation, printing and execution of the Cer-
               tificates, Indenture, Registration Statement and
               other documents relating to the Trust, Federal
               and State registration fees and costs, the ini-
               tial fees and expenses of the Trustee, legal and
               auditing expenses and other out-of-pocket organ-
               izational expenses, to the extent not borne by
               the Sponsor, shall be paid by the Trust;"

          D.   The third paragraph of Section 3.05 is hereby
     amended to add the following sentence after the first sen-
     tence thereof:  "Depositor may direct the Trustee to in-
     vest the proceeds of any sale of Securities not required
     for the redemption of Units in eligible money market in-
     struments selected by the Depositor which will include
     only negotiable certificates of deposit or time deposits
     of domestic banks which are members of the Federal Deposit
     Insurance Corporation and which have, together with their
     branches or subsidiaries, more than $2 billion in total
     assets, except that certificates of deposit or time depos-
     its of smaller domestic banks may be held provided the de-
     posit does not exceed the insurance coverage on the in-
     strument (which currently is $100,000), and provided fur-
     ther that the Trust's aggregate holding of certificates of
     deposit or time deposits issued by the Trustee may not ex-
     ceed the insurance coverage of such obligations and U.S.
     Treasury notes or bills (which shall be held until the ma-
     turity thereof) each of which matures prior to the earlier
     of the next following Distribution Date or 90 days after
     receipt, the principal thereof and interest thereon (to
<PAGE>





                              -3-


     the extent such interest is not used to pay Trust ex-
     penses) to be distributed on the  earlier of the 90th day
     after receipt or the next following Distribution Date."

          E.   The first sentence of each of Sections 3.10,
     3.11 and 3.12 is amended to insert the following language
     at the beginning of such sentence, "Except as otherwise
     provided in Section 3.13,".

          F.   The following new Section 3.13 is added:

          Section 3.13.  EXTRAORDINARY EVENT - SECURITY RETEN-
     TION AND VOTING.  In the event the Trustee is notified of
     any action to be taken or proposed to be taken by holders
     of the securities held by the Trust in connection with any
     proposed merger, reorganization, spin-off, split-off or
     split-up by the issuer of stock or securities held in the
     Trust, the Trustee shall take such action or refrain from
     taking any action, as appropriate,  so as to insure that
     the securities are voted as closely as possible in the
     same manner and in the same general proportion as are the
     securities held by owners other than the Trust.  If stock
     or securities are received by the Trustee, with or without
     cash, as a result of any merger, reorganization, spin-off,
     split-off or split-up by the issuer of stock or securities
     held in the Trust, the Trustee at the direction of the De-
     positor may retain such stock or securities in the Trust.
     Neither the Depositor nor the Trustee shall be liable to
     any person for any action or failure to take action with
     respect to this section.

          G.   Section 1.01 is amended to add the following
     definition:  (9) "Deferred Sales Charge" shall mean any
     deferred sales charge payable in accordance with the pro-
     visions of Section 3.12 hereof, as set forth in the pro-
     spectus for a Trust.  Definitions following this defini-
     tion (9) shall be renumbered.

          H.   Section 3.05 is hereby amended to add the fol-
     lowing paragraph after the end thereof:  On each Deferred
     Sales Charge payment date set forth in the prospectus for
     a Trust, the Trustee shall pay the account created pursu-
     ant to Section 3.12 the amount of the Deferred Sales
     Charge payable on each such date as stated in the prospec-
     tus for a Trust.  Such amount shall be withdrawn from the
     Principal Account from the amounts therein designated for
     such purpose.
<PAGE>





                              -4-



          I.   Section 3.06B(3) shall be amended by adding the
     following:  "and any Deferred Sales Charge paid".

          J.   Section 3.08 shall be amended by adding the fol-
     lowing at the end thereof:  "In order to pay the Deferred
     Sales Charge, the Trustee shall sell or liquidate an
     amount of Securities at such time and from time to time
     and in such manner as the Depositor shall direct such that
     the proceeds of such sale or liquidation shall equal the
     amount required to be paid to the Depositor pursuant to
     the Deferred Sales Charge program as set forth in the pro-
     spectus for a Trust.

          K.   Section 3.12 shall be added as follows:

          Section 3.12.  DEFERRED SALES CHARGE.  If the pro-
     spectus for a Trust specifies a Deferred Sales Charge, the
     Trustee shall, on the dates specified in and as permitted
     by the prospectus, withdraw from the Income Account if
     such account is designated in the prospectus as the source
     of the payments of the Deferred Sales Charge, or to the
     extent funds are not available in that account or if such
     account is not so designated, from the Principal Account,
     an amount per Unit specified in the prospectus and credit
     such amount to a special, non-Trust account maintained at
     the Trustee out of which the Deferred Sales Charge will be
     distributed to the Depositor.  If the Income Account is
     not designated as the source of the Deferred Sales Charge
     payment or if the balances in the Income and Principal Ac-
     counts are insufficient to make any such withdrawal, the
     Trustee shall, as directed by the Depositor, either ad-
     vance funds, if so agreed to by the Trustee, in an amount
     equal to the proposed withdrawal and be entitled to reim-
     bursement of such advance upon the deposit of additional
     monies in the Income Account or the Principal Account,
     sell Securities and credit the proceeds thereof to such
     special Depositor's account or credit Securities in kind
     to such special Depositor's Account.  Such directions
     shall identify the Securities, if any, to be sold or dis-
     tributed in kind and shall contain, if the Trustee is di-
     rected by the Depositor to sell a Security, instructions
     as to execution of such sales.  If a Unit Holder redeems
     Units prior to full payment of the Deferred Sales Charge,
     the Trustee shall, if so provided in the prospectus, on
     the Redemption Date, withhold from the Redemption Price
     payment to such Unit Holder an amount equal to the unpaid
     portion of the Deferred Sales Charge and distribute such
     amount to such special Depositor's account or, if the De-

<PAGE>





                              -5-


     positor shall purchase such Unit pursuant to the terms of
     Section 5.02 hereof, the Depositor shall pay the Redemp-
     tion Price for such Unit less the unpaid portion of the
     Deferred Sales Charge.  The Depositor may at any time in-
     struct the  Trustee to distribute to the Depositor cash or
     Securities previously credited to the special Depositor's
     account.

                              II.

             SPECIAL TERMS AND CONDITIONS OF TRUST

          The following special terms and conditions are hereby
agreed to:

          A.   The Trust is denominated Dean Witter Select Eq-
uity Trust, Morgan Stanley Competitive Edge Best Ideas October
1997 (the "Competitive Edge Trust").

          B.   The publicly traded stocks listed in Schedule A
hereto are those which, subject to the terms of this Indenture,
have been or are to be deposited in trust under this Indenture.

          C.   The term, "Depositor" shall mean Dean Witter
Reynolds Inc.

          D.   The aggregate number of Units referred to in
Sections 2.03 and 9.01 of the Basic Agreement is        for the
Select 10 Trust.

          E.   A Unit is hereby declared initially equal to
1/      th for the Competitive Edge Trust.

          F.   The term "In-Kind Distribution Date" shall mean
           ,     .

          G.   The term "Record Dates" shall mean            ,
    ,              ,     ,             ,      and            ,
     and such other date as the Depositor may direct.

          H.   The term "Distribution Dates shall mean         
  ,     ,             ,     ,              ,      and          
  ,      and such other date as the Depositor may direct.

          I.   The term "Termination Date" shall mean        ,
    .
<PAGE>





                              -6-

          J.   For purposes of this Series -- Dean Witter Se-
lect Equity Trust, Morgan Stanley Competitive Edge Best Ideas
October 1997 -- the form of Certificate set forth in this In-
denture shall be appropriately modified to reflect the title of
this Series and such of the  Special Terms and Conditions of
Trust set forth herein as may be appropriate.

          K.   The Depositor's Annual Portfolio Supervision Fee
shall be a maximum of $0.25 per 100 Units.

          L.   The Trustee's Annual Fee as defined in Section
6.04 of the Indenture shall be $     per 100 Units.

          M.   For a Unit Holder to receive "in-kind" distribu-
tion, such Unit Holder must tender at least 2,500 Units for re-
demption, either during the life of the Trust, or at its termi-
nation.

      (Signatures and acknowledgments on separate pages)



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