Vol. 3 of the New York State Firearms Trade books (Swinney/Rowe) cites a Thomas Medbery, New Berlin, ca. 1795-1818; Erieville, 1818-1828; ?Jefferson Co., late 1820's; Canton, 1830. (b.June 16, 1774; d. 1834(?). One of his rifles is illustrated along with further biographical information. His nephew, Joseph Medbery(Jr.) is also listed along with several examples of his firearms.
Hope this is of help.
Steve