Terry Moherek, president of the Cooper Memorial Library Association, said the penny postcard was found among the photos, maps, papers and other items donated to the library in Clermont and experts have said the autograph appears genuine, the Orlando (Fla.) Sentinel reported Wednesday.
"We don't know where it come from or who gave it to us," Moherek said. "When we first saw it, I thought, 'Oh, wonderful!'"
However, Moherek said the item has been "damaged" by someone tracing over part of the "B" and making markings above the signature.
Babe Ruth, whose real name was George Herman Ruth, hit 714 home runs during his 1914-1935 baseball career, most of which was spent with the New York Yankees.