A nice piece with well preserved details.
Obverse: head of Augustus in laurel wreath, to the right, in the rim legend:
CONSTAN-TINVS AVG;
Reverse: camp gate of 6 rows of bricks, with open gate, in the rim legend:
PROVIDEN-TIAE AVGG; in PTR section;
Bronze, diameter 17 mm, weight 3.26 g, axis 6 h.