This is really cool. From Science Daily:
Lydia Smith, a first-year psychology major from Granville, Ohio, was transcribing a letter written by Lincoln on Oct. 5, 1863, for a class project when she noticed a smudge that she suspected could be the 16th president’s thumbprint. Lincoln historians have confirmed the print.
A student at Miami University has discovered what experts say is a fingerprint belonging to Abraham Lincoln from nearly 150 years ago.