Constantius II. AE3 Alexandria, A.D. 348-350. 

D N CONSTAN-TIVS P F AVG, pearl-diademed, draped and cuirassed bust right.
FEL TEMP RE-PARATIO, soldier standing left, spearing fallen
horseman; 
Gamma in left field.
Mintmark ALEA. 

RIC VIII Alexandria 72; LRBC 2836.