Constantine I AE Follis. 320 AD. Trier. 

CONSTAN-TINVS AVG, helmeted, cuirassed bust right
VIRTVS-EXERCIT, trophy standing on ground, captive seated on 
either side

Mintmark dot PTR. 

RIC VII Trier 258. Extremely rare (R4). 

Note: officina P has the dot in the mintmark, officina S has no dot.

With permission of Roma Numismatics, July 2010