A nice piece.
Obverse: head of Augustus in a pearl diadem, to the right, in the rim legend:
CONSTAN-TINVS AVG;
Reverse: camp gate of 5 rows of bricks, with open gate, in the rim legend:
PROVIDEN-TIAE AVGG; in fields S-F, in segment SCONST;
Bronze, diameter 19 mm, weight 2.66 g, axis 12 h.