Constantine I. AE Follis. Trier. 325-326 AD. 

CONSTAN-TINVS AVG, laureate head right
PROVIDEN-TIAE AVGG, campgate, 6 layers, 2 turrets, star above, 
no doors. 

Mintmark PTR crescent. 

RIC VII Trier 461. Extremely rare (R4). 

With permission of Roma Numismatics, March. 2010