Constantius II, AE18, Thessalonica.

DN CONSTAN-TIVS PF AVG, pearl diademed, draped, cuirassed bust right.
FEL TEMP-REPARATIO, soldier standing left, right knee
raised, spearing fallen horseman who is reaching 
backwards, wearing a Phrygian helmet.
B in left field.
Mintmark SMTS.

RIC VIII Thessalonica 189 var (headwear). RIC lists only bare-headed horseman.

From Dane's collection, Dec. 2015.