It is circa AD 354-361 (AE3 if circa 18mm or less) of probably Constantius II as per SEARS(88) 4010. Obverse is: DN CONST[AN]-TIV[S PF AVG] Diadem, Draped and Cuirassed bust right. Reverse is [FEL TEM]P REPARATIO Soldier advancing left, spearing fallen horseman. The mint mark in the exergue is ASIS for Siscia (Sisak, Croatia).