A nice piece with visible remnants of silver plating.
Obverse: head of Augustus in laurel wreath, to the right, in the rim legend:
CONSTAN-TINVS AVG;
Reverse: camp gate of 9 rows of bricks, with open gate, in the rim legend:
PROVIDEN-TIAE AVGG; in SMANTB section;
Bronze, diameter 18 x 20 mm, weight 2.69 g, axis 12 h.