Constantine I. AE Follis. 310-313 AD. 

IMP CONSTANTINVS PF AVG, laureate, cuirassed bust right
MARTI PATRI PROPVGNATORI, Mars, helmeted, advancing right,
 holding transverse spear, shield on left arm. 

T-F across fields, PTR in ex. 

RIC VI Trier 833. Rated scarce.

With permission of Roma Numismatics, August, 2009