A very nice piece.
Obverse: bust of the emperor in laurel wreath, armor and paludamentum, to the right, in the rim legend:
M ANTONINVS PIVS AVG BRIT.
Reverse: Hercules standing naked left, holding olive branch, lion skin and mace, surrounded by legend:
P M TR P XV COS III P P;
Silver, diameter 17.5 x 19 mm, weight 3.16 g, axis 12 h.