Behind the ear, at the base of the hairline, note the straight line; which must have been an engraving aid.
Crispus
A.D. 324-325
19mm 3.1gm
FL IVL CRISPVS NOB CAES; Laureate, draped and cuirassed bust left.
PROVIDEN-TIAE CAESS; camp gate with two turrets and star between them.
in ex. SMNB
RIC VII Nicomedia 91