The obverse legend is probably
DN CONSTAN ─ TIVS P F AVG (pictures too small to say for sure), so this is Constantius as emperor who ruled from 337 to 361 (also Caesar = heir under his father Constantine the great until 337, when he is styled NOB. CAES.).
The reverse is to the common
GLORIA EXERCITVS type ("glory of the army"). The mintmark identifies this as having been struck in Constantinopolis.
EDIT: I think
this is it in the catalogue. So I think your mintmark is CONSΓ.
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