Constantine I, AE follis, London, 318 AD. 

CONSTANTINVS PF AVG, laureate, cuirassed bust right.
CLARITAS REIPBVLICAE, Sol standing left, chlamys 
across left shoulder, holding globe, right hand raised.
Crescent in left field.
Mintmark PLN

RIC VII London 125.
Extremely rare (R5)

With permission of ArtCoins Roma, Auction 6, Dec. 2012.