Constantius II AE3. Nicomedia.

Obv: FL IVL CONSTANTIVS NOB C, Laureate, draped and cuirassed bust left.
Rev: PROVIDENTIAE CAES dot, campgate, 7 layers, 2 turrets, star above.

Mintmark SMNB

With permission of Roma Numismatics, April, 2011

Known mintmarks for this issue:
SMNB
SMN delta
SMN epsilon
SMNS