A very nice piece. Patina.
Obverse: bust of the emperor in laurel wreath, armor and paludamentum, to the right, in the rim legend:
CONSTANTINVS IVN NOB C;
Reverse: camp gate, surrounded by legend:
PROVIDEN-TIAE CAESS, in segment SMHGamma-;
Bronze, diameter 18 mm, weight 3.06, axis 11 h.