According to David E. Schenkman's Civil War Sutler Tokens and Cardboard Scrip, M. Sullivan apparently was a sutler with the 57th Regiment of the Ohio Volunteer Militia prior to becoming a sutler for the 55th Regiment. Tokens for both were struck from the same dies, with the "7" of "57" being reengraved to a "5."
Your token is rated R7— between 11 and 20 known at the time of the book's publication (1983).