Magnentius, AE2, 25 mm, Rome. AD 340-350. 

DN MAGNEN-TIVS PF AVG, bare-headed, draped, cuirassed bust right, A behind head.
GLORIA ROMANORVM, emperor on horseback galloping right, no 
shield, wielding spear at a bare-headed enemy half-kneeling 
before the horse, broken spear and shield beneath the horse. 
Star in upper right field. 
Mintmark RS. 

RIC VIII Rome 197; Cohen 20. 

With permission of cgb.fr Mail Bid Sale 43, Lot 1022, April 2010.