This coin looks just like Rome 165, except for the open doors. RIC 190 has open doors, but four turrets instead of three.
Constantine I
A.D. 318- 319
18x20mm 3.0gm
CONST-ANTINVS AVG, helmeted and cuirassed bust right.
VIRTV-S AVGG, campgate with open doors and arched doorway, with three turrets.
In ex. RP, in fields P/R
Cf RIC VII Rome 165