A nice piece. Patina, tarnish.
Obverse: bust of emperor wearing radial crown, armor and paludamentum, to right, surrounded by legend:
IMP CAES MANT GORDIANVS AVG
Reverse: Mars standing right, holding spear and shield, in the rim legend:
PM TR P II COS P P
Silver, diameter 20.5 x 21.5 mm, weight 5.49 g, axis 6 h.