I just won this on ebay, so the specs & pic belong to the seller.
Coin is:
AE2 25mm 5g
OBV: DN CONSTAN - TIVS PF AVG; pearl diademed draped cuirassed bust holding globe in right hand r.
REV: FEL TEMP RE - PARATIO; soldier spearing fallen horseman w/ phrygian cap
EXE: TSE*
REF: RIC VIII Thessalonica 115, rated S.
This is a rare bust type, G3 r. present just at Rome and Thessalonica for both Constantius II & Constans (G3 l. is well known for hutt & captives and emperor & captives), which makes this a rather rare coin, much rarer than RIC's rating. Can't find another being offered for sale.