A nice piece.
Obverse: head of Augustus in laurel wreath, to the right, in the rim legend:
CONSTAN-TINVS AVG;
Reverse: camp gate of 7 rows of bricks, with open gate, in the rim legend:
PROVIDEN-TIAE AVGG; in SMANTB section;
Bronze, diameter 21 mm, weight 2.49 g, axis 5 h.