Constantine I AE follis. 

Obv: CONSTAN-TINVS AVG, laureate head right 
Rev: VIRTV-S AVGG, campgate, 4 turrets, 5 layers, star above, 
open panelled doors.
Mintmark: SA crescent RL 

RIC VII Arles 291; Sear 16307.

Sold for $71.
CNG ebay sale, May 2000.