Nicomedia, is a slightly more unusual mint, or at least it is over here.Outstanding find !!
Constantius II, AR Siliqua, Nicomedia, AD 341-351. DN CONSTAN
TIVS PF AVG, pearl-diademed head right / VOTIS-XXV-MVLTIS XXX in 4 lines within laurel wreath. Mintmark: SMN (`Nicomedia now Izmit, Turkey). RIC VIII Nicomedia 40; RSC 340.
Don in SoCal.