Here is a really nice example of this type.
Constantine I
A.D. 318-9
19mm 3.2gm
CONST-ANTINVS AVG, helmeted and cuirassed bust right.
ROMAE AETERNAE [To everlasting Rome, fifteen yearly vows (quindecennalia)] Roma std. r., shield in lap inscribed X/V, in fields P/R
in ex. RS
RIC VII Rome 146
