Johannes, AE4, Rome. AD 423-425. 
(DN IOH)AN-N)ES PF AVG), pearl-diademed, draped and cuirassed bust right.
SALVS REI-PVBLICAE, Victory advancing left, trophy on shoulder, dragging captive behind her. 
Chi-rho in left field. 
Mintmark RMS

RIC X 1913, with officina letter (sometimes omitted).
Very rare (R3-R4)

RIC notes the mintmark RM and that the officina letter is
sometimes omitted. This coin clearly has the off. letter S