Constantine I, AE follis, AD 318-319, Rome. 19mm, 2.85 g. 

CONS-TANTINVS AVG, cuirassed bust right, wearing laureate, high-crested helmet.
VIRTV-S AVGG, campgate, six layers, three turrets, closed,
panelled doors. 

P-R across fields. 
Mintmark RT. 

RIC VII Rome 176.
Rare - rated R4.
Unlisted obv. break.

With permission of Auktionshaus H. D. Rauch GmbH, Sept. 2011.