Constantine I (A.D. 307 - 337), AE Follis, Lyons, 

Obv: IMP CONSTANTINVS PF AVG, laureate, cuirassed bust right.
Rev: MARTI CON-SERVATORI, Mars, helmeted, chlamys across left shoulder,
holding upright spear, point downwards and resting left hand on shield.

T-F across fields.
Mintmark PLG.

RIC VII Lyons 12, rated R3

Courtesy of TimeLine Originals (www.time-lines.co.uk), March, 2011