Constantius II, AE3. Nicomedia.

DN CONSTAN-TIVS PF AVG, pearl diademed, draped, cuirassed bust right.
FEL TEMP RE-PARATIO, soldier spearing fallen horseman who is
bearded, wearing a bowl-shaped, brimmed helmet, reaching
backwards.
Gamma in left field.
Mintmark dot SMN epsilon.

RIC VIII Nicomedia 86 var (headwear).
Scarce.

RIC lists only the Phrygian helmet ("pointed cap") as headwear
for this Nicomedia series. However, a number of different 
headwear types and hairstyles have been seen from Nicomedia.

from Dane's collection, ex-cerberuscoins.com, Aug. 2011