Constantine AE 24mm Follis. 313-315 AD.  

Obv: CONSTANTINVS PF AVG, laureate, cuirassed bust right
Rev: MARTI CONSERVATORI, Mars, helmeted, in military 
dress, standing right, holding spear and resting left 
hand on shield. T-F across fields, PTR in ex. 

RIC VII 53, very rare (R3)

With permission of Roma Numismatics, June 2009