Constantine II, AE follis, Lyons. AD 324-325. 

CONSTANTINVS IVN NOB C, laureate, draped, cuirassed bust left, seen from the back.
PROVIDEN-TIAE CAESS, campgate, six layers, two turrets, star
above, no doors.

Mintmark PLG.

RIC VII Lyons 229.
Rare, rated R3.