Constantius II (337-361 A.D.) - AE2 Centenionalis  - 20.29x19.68mm, 4.39gr
Obverse - DN CONSTAN-TIVS PF AVG
Constantius, his pearl diademed, draped and cuirassed bust right.
Delta behind bust.
Reverse - FEL TEMP RE-PARATIO.
ASIRM in Exergue. 
Helmeted soldier advancing left, with shield on left arm, spearing falling horseman;
shield on ground to right. Horseman is bearded and bare-headed; he turns to face
soldier and extends right arm.
Constantius II
The image below was photographed by Vaughn Rare Coin Gallery. The image above is my own scan.
Minted at the first officina in Sirmium (Sremska Mitrovica, Serbia) in 353 A.D.
Reference:
Kent, J.P.C., "Roman Imperial Coinage", Volume 8 (RIC), Sirmium, p387, nr 35, obverse Cs1, bust D3
Sear, David R., "Roman Coins and their Values" (RCV 4th Revised Edition), p337, nr. 4003, variation from Sirmium mint
Failmezger, V., "Roman Bronze Coins From Paganism To Christianity 294-364 A.D.", nr 462b14-b17CS, variation without reverse field mark
Carson, R.A.G., Hill, P.V., & Kent, J.P.C., "Late Roman Bronze Coinage",  Part II, p76, nr 1594
Van Meter, D., "Handbook of Roman Imperial Coins", p300, nr 90
Suarez, R., "Encyclopedia of Roman Imperial Coins" (ERIC),  p494, nr.86, variation M14 (B08, O13, R11, T67, M14, Exe: ASIRM)
Quality: Obverse: Very Fine+ / Reverse: Very Fine