Constantius II, AE3, Arles. 

DN CONSTAN-TIVS PF AVG, pearl diademed, draped, cuirassed bust right.
FEL TEMP-REPARATIO, soldier standing left, spearing fallen horseman who is
wearing a bowl-shaped helmet, and reaching backwards.
M in centre.
Mintmark SCON.

RIC VIII Arles 272 var (horseman's headwear). Rated R2.

From Dane's collection, July 2012.