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                                                                   EXHIBIT 10.15

                               April 17, 2007

Tailwind Financial Inc.
BCE Place, 181 Bay Street, Suite 2040
Toronto, Ontario, Canada M5J 2T3


     Re: INITIAL PUBLIC OFFERING


Ladies and Gentlemen:


     This letter is being delivered to you in accordance with the Underwriting
Agreement (the "UNDERWRITING AGREEMENT") entered into by and between Tailwind
Financial Inc., a Delaware corporation (the "COMPANY"), and Deutsche Bank
Securities Inc. (the "UNDERWRITER"), relating to an underwritten initial public
offering (the "IPO") of the Company's units (the "UNITS"), each Unit comprised
of one share of the Company's common stock, par value $0.001 per share (the
"COMMON STOCK"), and one warrant, which is exercisable for one share of Common
Stock. Certain capitalized terms used herein are defined in paragraph 11 hereof.

     In order to induce the Company and the Underwriter to enter into the
Underwriting Agreement and to proceed with the IPO, and in recognition of the
benefit that such IPO will confer upon the undersigned as a stockholder of the
Company, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the undersigned hereby agrees with
the Company and the Underwriter as follows:

1.   If the Company solicits approval of its stockholders of a Business
Combination, the undersigned will vote all Insider Shares owned by him in
accordance with the majority of the votes cast by the holders of the IPO Shares.

2.   In the event that the Company fails to consummate a Business Combination
within eighteen (18) months from the effective date (the "EFFECTIVE DATE") of
the Registration Statement (or twenty-four (24) months from the Effective Date
under the circumstances described in the Registration Statement), the
undersigned will take all reasonable actions within the undersigned's power to
(i) cause the Trust Account to be liquidated and distributed to the holders of
IPO Shares in accordance with that Investment Management Trust Agreement to be
entered into by and among the Company, Deutsche Bank Securities Inc. and
American Stock Transfer & Trust Company, as Trustee; and (ii) cause the Company
to liquidate as soon as reasonably practicable. The undersigned hereby waives
any and all right, title, interest or claim of any kind in or to (x) any
distribution of the Trust Account with respect to the undersigned's Insider
Shares

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and Common Stock underlying the Private Placement Warrants in connection with a
liquidation and (y) any remaining net assets of the Company after such
liquidation.

3.   Except as disclosed in the Registration Statement, none of the undersigned,
any member of the family of the undersigned, nor any Affiliate of the
undersigned will be entitled to receive and will not accept any compensation for
services rendered to the Company prior to or in connection with the consummation
of the Business Combination; PROVIDED THAT the undersigned shall be entitled to
reimbursement from the Company for the undersigned's out-of-pocket expenses
incurred in connection with seeking and consummating a Business Combination.

4.   None of the undersigned, any member of the family of the undersigned, nor
any Affiliate of the undersigned will be entitled to receive or accept from the
Company a finder's fee or any other compensation in the event the undersigned,
any member of the family of the undersigned or any Affiliate of the undersigned
originates a Business Combination.

5.   The undersigned shall escrow (i) the undersigned's Insider Shares (if any)
until the first anniversary of the consummation of the Business Combination and
(ii) the undersigned's Private Placement Warrants (if any) and any shares of
Common Stock issued upon exercise thereof until ninety (90) days after
consummation of a Business Combination, in each case subject to the terms of a
Securities Escrow Agreement which the Company will enter into with the
undersigned and American Stock Transfer & Trust Company, as escrow agent, in
form and substance acceptable to the Company.

6.   The undersigned agrees to be a director of the Company and currently
intends to serve until the earlier of the consummation by the Company of a
Business Combination or the liquidation of the Company. The undersigned's
Questionnaire for Directors, Officers and Principal Stockholders furnished to
the Company and attached hereto as EXHIBIT A and the biographical information in
the Registration Statement is true and accurate in all respects and does not
omit any material information with respect to the undersigned's background. The
undersigned's NASD Questionnaire furnished to Deutsche Bank Securities Inc. and
annexed as EXHIBIT B hereto is true and accurate in all respects. The
undersigned represents and warrants that:

     6.1     the undersigned is not subject to, or a respondent in, any legal
action for, any injunction, cease-and-desist order or order or stipulation to
desist or refrain from any act or practice relating to the offering of
securities in any jurisdiction;

     6.2     the undersigned has never been convicted of or pleaded guilty to
any crime (i) involving any fraud or (ii) relating to any financial transaction
or handling of funds of another person, or (iii) pertaining to any dealings in
any securities and he is not currently a defendant in any such criminal
proceeding;

     6.3     the undersigned has never been suspended or expelled from
membership in any securities or commodities exchange or association or had a
securities or commodities license or registration denied, suspended or revoked;

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     6.4     a petition under any federal bankruptcy laws or any state,
territorial or provincial insolvency law was not filed by or against, nor was a
receiver, fiscal agent or similar officer appointed by a court for the business
or property of the undersigned, or for any partnership in which the undersigned
was a general partner within the past two years, or for any corporation or
business association of which the undersigned was an executive officer within
the past two years;

     6.5     the undersigned has not been subject to any order prohibiting and
is not subject to any legal proceeding seeking to prohibit him or her from
engaging in any type of business practice;

     6.6     the undersigned has not been found by a court of competent
jurisdiction in a civil action by the Securities and Exchange Commission or by
any other federal, state, territorial or provincial administrative or regulatory
authority to have violated any federal, state, territorial or provincial
securities law; and

     6.7     the undersigned has not been found by a court of competent
jurisdiction in a civil action by the Commodity Futures Trading Commission or by
any other federal, state, territorial or provincial administrative or regulatory
authority to have violated any federal, state, territorial or provincial
commodities law.

7.   The undersigned agrees that until the earlier of (i) the consummation of a
Business Combination or the liquidation of the Company or (ii) such time as the
undersigned ceases to be an officer or director of the Company, (X) the
undersigned shall present to the Company for its consideration, prior to
presentation to any other entity, any business opportunity which may reasonably
be deemed appropriate for the Company based on the description in the
Registration Statement of the Company's proposed business or which is required
to be presented to the Company under Delaware law subject to any pre-existing
fiduciary or contractual obligations the undersigned has and (Y) the undersigned
shall not assist or participate with any other person or entity in the pursuit
of or negotiation with respect to such business opportunity unless and until it
receives written notice from the Company that the Company has determined not to
pursue such business opportunity.

8.   The undersigned authorizes any employer, financial institution, or consumer
credit reporting agency to release to the Company and its legal representatives
or agents (including any investigative search firm retained by the Company) any
information he or it may have about the undersigned's background and finances
("INFORMATION"), provided that the Information is used solely to determine the
truth and accuracy of the undersigned's representations hereunder and the
disclosure in the Registration Statement and for no other purpose; provided
further that the Company shall use all reasonable efforts to keep the
Information confidential and shall not disclose the Information to any other
person or entity without the prior written consent of the undersigned, unless
such disclosure (i) is required by law or regulation or requested in connection
with a judicial proceeding or governmental investigation or (ii) was disclosed
in the Registration Statement. Neither the Company nor its agents shall be
violating the undersigned's right of privacy in any manner in requesting and
obtaining the Information and the

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undersigned hereby releases them from liability for any damage whatsoever in
that connection.

9.   This letter agreement shall be binding on the Company and the undersigned
and the undersigned's respective successors, heirs, personal representatives and
assigns. This letter agreement shall terminate on the earlier of (i) the date
upon which the Business Combination is consummated and (ii) the date upon which
the liquidation and distribution of the Trust Account is completed, provided
that the following Sections shall survive such termination: 3, 4, 5, 9, 10,
11, and 12.

10.  This letter agreement shall be governed by and construed and enforced in
accordance with the laws of the State of New York, without giving effect to
conflicts of law principles that would result in the application of the
substantive laws of another jurisdiction. Each of the Company and the
undersigned hereby (i) agrees that any action, proceeding or claim against him
or it arising out of or relating in any way to this letter agreement shall be
brought and enforced in the courts of the State of New York or the United States
District Court for the Southern District of New York, and irrevocably submits to
such jurisdiction, which jurisdiction shall be exclusive, and (ii) waives any
objection to such exclusive jurisdiction and that such courts represent an
inconvenient forum.

11.  As used herein:

     11.1    "AFFILIATE" shall have the meaning ascribed to it in Rule 12b-2 of
the General Rules and Regulations under the Securities Exchange Act of 1934, as
amended.

     11.2    "BUSINESS COMBINATION" shall mean the Company's initial acquisition
of one or more assets or operating businesses through a merger, capital stock
exchange, asset or stock acquisition, exchangeable share transaction or other
similar business combination.

     11.3    "INSIDERS" shall mean all officers and directors of the Company
immediately prior to the IPO and each of the following:

     Gordon A. McMillan
     Andrew A. McKay
     Robert Penteliuk
     Robert C. Hain
     Stephen T. Moore
     TFC Holdings Ltd.
     Parkwood Holdings Ltd.
     JovFunds Management Inc.

     11.4    "INSIDER SHARES" shall mean all of the shares of Common Stock of
the Company owned by an Insider prior to the IPO.

     11.5    "IPO SHARES" shall mean the shares of Common Stock comprising the
Units issued in the Company's IPO.

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     11.6    "PRIVATE PLACEMENT WARRANT" shall mean up to 4,700,000 warrants of
the Company purchased in a private placement prior to and subject to
consummation of the IPO.

     11.7    "REGISTRATION STATEMENT" shall mean the registration statement
filed by the Company on Form S-1 (No. 333-135790) with the Securities and
Exchange Commission on July 14, 2006, and any amendment or supplement thereto,
in connection with the IPO.

     11.8    "TRUST ACCOUNT" shall mean the trust account established with
American Stock Transfer & Trust Company, the amounts therein to be released
only in the event of either the consummation of a Business Combination or a
liquidation of the Company except for up to $1,600,000 of interest earned
(net of taxes) which will be released to the Company to fund a portion of
their working capital expenses.

12.  No term or provision of this letter agreement may be amended, changed,
waived, altered or modified except by written instrument executed and delivered
by the undersigned and the Company.


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                                           Sincerely,

                                             /s/ Philip Armstrong
                                           ----------------------------------
                                           Name: Philip Armstrong


Accepted and agreed:

TAILWIND FINANCIAL INC.

By: /s/ Andrew A. McKay
    ---------------------------
Name:  Andrew A. McKay
Title: President and Chief Executive Officer

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   EXHIBIT A: QUESTIONNAIRE FOR DIRECTORS, OFFICERS AND PRINCIPAL STOCKHOLDERS

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                          EXHIBIT B: NASD QUESTIONNAIRE