It's Constantine I...his son Constantius II never issued this type. Compare with the example below. I am not sure if your coin is cuirassed only though. The workshop of your coin is not clear either. The mintmark is R star (?) with possible workshops being P,S,T, or Q.

Constantine I
A.D. 314
20mm 3.9gm
IMP CONSTANTINVS PF AVG, laureate, draped and cuirassed
SOLI INVIC-TO COMITI, Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, across fields R-F
In ex. R star S
RIC VII Rome 19

Constantine I
A.D. 314
20mm 3.9gm
IMP CONSTANTINVS PF AVG, laureate, draped and cuirassed
SOLI INVIC-TO COMITI, Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, across fields R-F
In ex. R star S
RIC VII Rome 19

























