Constantine II, Rome, AE 3. 318-319 AD. 3.52 g.

CONSTANTINVS IVN NOB C, Laureate, draped, cuirassed bust right.
ROMAE AETERNAE, Roma seated right on shield, inscribing X-V 
on shield on her lap.
P-R across fields.
Mintmark RT.

RIC VII Rome 156, rated R3