Constantine I AE follis, Arles, AD 326-327. 

CONSTANTINVS AVG, laureate head right.
PROVIDEN-TIAE AVGG, campgate, nine layers, two turrets, 
star above, 

S-F across fields.
Mintmark PARL.

RIC VII Arles 301; Sear 16245.

Very rare, rated R4.

With permission of Zach of beastcoins.com.