Constantius II, AE2, Constantinople.

DN CONSTAN-TIVS PF AVG, pearl diademed, draped, cuirassed bust right.
FEL TEMP RE-PARATIO, soldier spearing fallen horseman who is wearing
a Phrygian helmet, no beard, clutching horse's neck.
Sigma in left field.
Mintmark CONSZ star

RIC VIII Constantinople 81 var (unlisted fieldmark)
Very rare. R4

Courtesy of Roma Numismatics, (item 10752), Feb 2011