Roman 'Mona Lisa' vessel applique, ca. 2nd-3rd Cent AD
Copper alloy; 46mm/26.2gm
Not exactly "the girl with the mystic smile", this vessel adornment started life on the wrong foot. Poorly forged to begin with, then lost or dis-guarded (possibly by the smith) and left in the ground for 1,800 years and slowly accumulating a very thick and almost mud-like green patina.
I have no clue as to which deity or personification this represents: your guess is as good as ours.