EXHIBIT 99.1

                                 REVOCABLE PROXY

                   GREENVILLE COMMUNITY FINANCIAL CORPORATION

                         SPECIAL MEETING OF SHAREHOLDERS

           THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS

     The undersigned hereby appoints William Ham and Ted Kortes, or either of
them, with full power of substitution, to act as attorneys and proxies for the
undersigned to vote all shares of common stock of Greenville Community Financial
Corporation ("GCFC") that the undersigned is entitled to vote at GCFC's Special
Meeting of Shareholders (the "Meeting"), to be held on December 17, 2007, at
2 p.m., local time, located at the Stanley & Blanche Ash Technology & Learning
Center (M-TEC Center), 1325 Yellow Jacket Drive, Greenville, Michigan, 48838 and
any and all adjournments and postponements thereof.

      The undersigned acknowledges receipt from GCFC, prior to the execution of
this proxy, of Notice of the Special Meeting and a Proxy Statement Prospectus.

                 (Continued and to be signed on following page)

                                 Exhibit 99.1 - 1


GREENVILLE COMMUNITY FINANCIAL CORPORATION

      1. Approval of the Agreement and Plan of Merger, dated as of August 21,
2007, and as amended on September 24, 2007 (the "Merger Agreement"), by and
between Greenville Community Financial Corporation and IBT Bancorp, Inc.

      [ ] For [ ] Against [ ] Abstain

      The Board of Directors recommends a vote "FOR" approval of the Merger
      Agreement.

      2. In accordance with their discretion, upon all other matters that may
properly come before said meeting and any adjournment or postponements of the
meeting, including without limitation, a motion to adjourn the special meeting
to another time or place.

      THIS PROXY WILL BE VOTED AS DIRECTED. IF NO DIRECTIONS ARE SPECIFIED, THIS
PROXY WILL BE VOTED FOR APPROVAL OF THE MERGER AGREEMENT. IF ANY OTHER BUSINESS
IS PRESENTED AT THE MEETING, THIS PROXY WILL BE VOTED BY THOSE NAMED IN THIS
PROXY IN THEIR JUDGMENT. AT THE PRESENT TIME, THE BOARD OF DIRECTORS KNOWS OF NO
OTHER BUSINESS TO BE PRESENTED AT THE MEETING.

                                Dated:____________________________________

                                Print Name:_______________________________

                                Signature:________________________________

                                Print Name:_______________________________

                                Signature:________________________________

                                Please sign exactly as your name appears on this
                                card. When signing as attorney, executor,
                                administrator, trustee or guardian, please give
                                your full title. If shares are held jointly,
                                each holder should sign.

                                YOUR VOTE IS IMPORTANT!

                                PLEASE PROMPTLY COMPLETE, SIGN AND MAIL THIS
                                PROXY IN THE ENCLOSED, POSTAGE-PAID ENVELOPE

                                 Exhibit 99.1 - 2