Constantine I as Caesar AE follis, 27 mm. Trier mint, 307 AD. 

FL VAL CONSTANTINVS NOB C, laureate, cuirassed bust right. 
MARTI PATRI PROPVGNATORI, Mars, naked except for helmet 
and chlamys, advancing right, holding spear and shield.
S-A across fields.
Mintmark PTR. 

RIC VI Trier 730. 

With permission of Roma Numismatics, Sept. 2012.