This is a fairly rare type first minted under the authority of Vetranio, but also struck two other times (when Gallus and Julian II are Caesar) and all are indentical according to RIC.
Constantius II
circa A.D. 350
18x19mm 2.2gm
DN CONSTANTIVS PF AVG, pearl-diademed, draped and cuirassed bust.
GLORIA ROMANORVM, Emperor, bare-headed and in military dress, stg. facing, head l., holding standard with Chi-Rho on the banner, and spear.
In ex. ΓSIS
RIC VIII Siscia 293, 355, 386