The leg belongs to Anne Bancroft (who was married to Mel Brooks later!).
She played Mrs. Robinson in “The Graduate”.
Dustin Hoffman was the recently minted college graduate, Ben Braddock, that she seduces.
Here’s the info on the film (1967):
http://www.imdb.com/title/tt0061722/?ref_=fn_al_tt_1
Right. Well, how could her leg wind up in a painting of Napoleon? Some manner of gag for a movie?