A nice piece.
Obverse: bust of Caesar in armor and paludamentum, wearing laurel wreath, to the right, in the rim legend:
CONSTANTINVS IVN NOB C;
Reverse: camp gate of 7 rows of bricks, with open gate, in the rim legend:
PROVIDEN-TIAE CAES-; in section MNGamma;
Bronze, diameter 19 mm, weight 2.13 g, axis 6 h.