Constantine I AE Follis, 4.24 gr, 23.53 mm. London. 312-313 AD.  

Obverse: CONSTANTINVS PF AVG, laureate and cuirassed bust right.  
Reverse: MARTI CON-SERVATORI, Mars, standing right, helmeted and in 
military dress, holding reversed, upright spear, left hand on shield; 

star in left field; 
mintmark PLN.  

RIC VI London 254, rated C2.

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