EXHIBIT 3.3


                              DORSEY & WHITNEY LLP
                               COUNSELORS AT LAW
                                250 Park Avenue
                               New York, NY 10177
                              Writer's Direct Dial
                                 (212) 415-9286
                              Fax: (212) 953-7201


                                 April 21, 2010


The Bank of New York,
as Trustee of

Claymore Securities Defined Portfolios, Series 680
CLOSED-END INCOME & TREASURY LIMITED DURATION PORTFOLIO, SERIES 7

2 Hanson Place
12th Floor
Brooklyn, New York  11217

Ladies and Gentlemen:

     We are acting as special New York tax counsel for purposes of determining
the applicability of certain New York taxes in connection with that certain
Reference Trust Agreement (the "Trust Agreement") dated as of today's date
between Claymore Securities, Inc. Fixed Income Securities, L.P. as Depositor
(the "Depositor") and The Bank of New York Mellon, as Trustee (the "Trustee"),
establishing Claymore Securities Defined Portfolios, Series 680, CLOSED-END
INCOME & TREASURY LIMITED DURATION PORTFOLIO, SERIES 7 ( the "Trust") and the
execution by the Trustee under the Trust Agreement, of receipts for units
evidencing ownership of all of the units of fractional undivided interest (such
receipts for units and such aggregate units being herein respectively called
"Receipts for Units" and "Units") in the Trust, as set forth in the prospectus,
(the "Prospectus") included in the registration statement on Form S-6, as
amended to the date hereof (the "Registration Statement"), relating to the
Trust. For purposes of this opinion, it is assumed that the assets of the Trust
(which we have not examined and express no opinion with respect to) will consist
of interests in qualified regulated investment companies (the "RICs") under the
Internal Revenue Code of 1986, as amended (the "Code"). The RICs held by the
Trust shall be referred to as the "Securities." We note that the Trust may hold
other assets. We express no opinion as to the effect of holding such other
assets on the conclusions reached herein. It is noted that no opinion is
expressed herein with regard to the federal tax aspects of the Securities, the
Trust, the Units or any interest, gains or losses in respect thereof.

     The Trustee did not participate in the selection of the Securities to be
deposited in the Trust, and, upon the receipt thereof, will cause the number of
Units representing the entire capital of the Trust to be deposited in the
Depositor's account at The Depository Trust Company, as more fully set forth in
the Prospectus. The Units, which are represented by book entry positions, will
be offered to the public upon the effectiveness of the Registration Statement.

     The duties of the Trustee, which are ministerial in nature, will consist
primarily of crediting the appropriate accounts with interest received by the
Trust and with the proceeds from the disposition of securities held in the Trust
and the distribution of such payments and proceeds to the Unit holders. The
Trustee will also maintain records of the registered holders of Units
representing an interest in the Trust and administer the redemption of Units by
such registered holders and may perform certain administrative functions with
respect to an automatic reinvestment option.

     Generally, Securities held in the Trust may be removed therefrom by the
Trustee at the direction of the Depositor upon the occurrence of certain
specified events which adversely affect the sound investment character of the
Trust, such as default by the issuer in payment of declared dividends or of
interest or principal on one or more of its debt obligations.

     Prior to the termination of the Trust, the Trustee is empowered to sell
Securities designated by the Depositor only for the purpose of redeeming Units
tendered to it and of paying expenses for which funds are not available. The
Trustee does not have the power to vary the investment of any Unit holder in the
Trust, and under no circumstances may the proceeds of sale of any Securities
held by the Trust be used to purchase new Securities to be held therein.

     Article 9-A of the New York Tax Law imposes a franchise tax on business
corporations. For purposes of that Article, Section 208.l(d) defines the term
"corporation" to include, among other things, "any business conducted by a
trustee or trustees wherein interest or ownership is evidenced by certificate or
other written instrument."

     The Regulations promulgated under Section 208 provide as follows:

     (b) The term corporation includes . . . any business conducted by a trustee
or trustees wherein interest or ownership is evidenced by certificate or other
written instrument.

     (2) A business conducted by a trustee or trustees in which interest or
ownership is evidenced by certificate or other written instrument includes, but
is not limited to, an association commonly referred to as a business trust or
Massachusetts trust. In determining whether a trustee or trustees are conducting
a business, the form of the agreement is of significance but is not controlling.
The actual activities of the trustee or trustees, not their purposes and powers,
will be regarded as decisive factors in determining whether a trust is subject
to tax under Article 9 A of the Tax Law. The mere investment of funds and the
collection of income therefrom with incidental replacement of securities and
reinvestment of funds, does not constitute the conduct of a business in the case
of a business conducted by a trustee or trustees. 20 NYCRR 1-2.5(b).

     New York cases dealing with the question of whether a trust will be subject
to the franchise tax have also delineated the general rule that where a trustee
merely invests funds and collects and distributes the income therefrom, the
trust is not engaged in business and is not subject to the franchise tax,
Burrell v. Lynch, 274 A.D. 347, 84 N.Y.S.2d 171 (3rd Dept, 1948), order
resettled, 274 A.D. 1073, 85 N.Y.S.2d 703 (3rd Dept. 1949).

     In an opinion of the Attorney General of the State of New York, 47 N.Y.
Att'y. Gen, Rep. 213 (Nov. 24, 1942), it was held that where the trustee of an
unincorporated investment Trust was without authority to reinvest amounts
received upon the sales of securities and could dispose of securities making up
the trust only upon the happening of certain specified events or the existence
of certain specified conditions, the trust was not subject to the franchise tax.
See also Fibreboard Asbestos Compensation Trust (Advisory Opinion) Commission of
Taxation and Finance, TSB-A-97(3)C and TSB-A-97(1)I, January 21, 1997.

     In the instant situation, the Trustee is not empowered to, and we assume
will not, sell Securities contained in the corpus of the Trust and reinvest the
proceeds therefrom. Further, the power to sell such Securities is limited to
circumstances in which the creditworthiness or soundness of the issuer of such
Security is in question or in which cash is needed to pay redeeming Unit holders
or to pay expenses, or where a Trust liquidated subsequent to the termination of
such Trust. In substance, the Trustee will merely collect and distribute income
and will not reinvest any income or proceeds, and the Trustee has no power to
vary the investment of any Unit holder in the Trust.

     Under Subpart E of Part I, Subchapter J of Chapter 1 of the Code the
grantor of a trust will be deemed to be the owner of the trust under certain
circumstances, and therefore taxable on his proportionate interest in the income
thereof. Where this federal tax rule applies, the income attributed to the
grantor will also be income to him for New York income tax purposes. See
TSB-M-78(9)C, New York Department of Taxation and Finance, June 23, 1978.

     By letter dated today, Chapman and Cutler LLP rendered its opinion that
each Unit holder will be considered as owning a share of each asset of a Trust
in the proportion that the number of Units held by such holder bears to the
total number of Units outstanding and the income of a Trust will be treated as
the income of each Unit holder in said proportion pursuant to Subpart E of Part
I, Subchapter J of Chapter 1 of the Code.

     Based on the foregoing and on the opinion of Chapman and Cutler LLP, dated
today, upon which we specifically rely, we are of the opinion that under
existing laws, rulings, and court decisions interpreting the laws of the State
and City of New York:

     1.   The Trust will not constitute an association taxable as a
          corporation under New York law, and, accordingly, will not be subject
          to tax on its income under the New York State franchise tax or the New
          York City general corporation tax.

     2.   The income for the Trust will be treated as the income of the
          Unit holders under the income tax laws of the State and City of New
          York.

     3.   Unit holders who are not residents of the State of New York are
          not subject to the income tax laws thereof with respect to any
          interest or gain derived from the Trust or any gain from the sale or
          other disposition of the Units, except to the extent that such
          interest or gain is from property employed in a business, trade,
          profession or occupation carried on in the State of New York.

     No opinion is expressed herein regarding the federal income tax aspects or
any other state or local tax aspects of the Trust, the Securities or the Units.
No opinion is expressed with respect to the taxation of the Trust, the
Securities or the Unit holders under any provisions of New York State or New
York City tax law except for the conclusions set forth above.

     We hereby consent to the filing of this opinion letter as an exhibit to the
Registration Statement relating to the Units and to the use of our name and the
reference to our firm in the Registration Statement and in the Prospectus. In
giving this consent, we do not thereby admit that we are included in the
category of persons whose consent is required under Section 7 of the Securities
Act of 1933 or the rules and regulations of the Securities and Exchange
Commission.


                                                               Very truly yours,

                                                        /s/ DORSEY & WHITNEY LLP

                                                            DORSEY & WHITNEY LLP