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This is an ancient Roman gold Solidus of emperor Theodosius II, who reigned from 408 - 450 A.D.
Obverse: DN THEODOSIVS PF AVG "Our Lord Theodosius, Dutiful and Wise Augustus" helmeted, cuirassed three-quarters-facing bust, spear over shoulder and shield decorated with horseman spearing enemy.
Reverse: CONCORDI-A AVGGS "Harmony of the Augusts" Constantinopolis seated facing with sceptre and Victory on globe
This coin was struck at the Constantinople mint, between the years 408 - 420 A.D. It bears the Officina letter S (for Secunda), SECVNDA on the end of the reverse legend after AVGG S, this indicates the coin to have been minted by the 2nd Officina at the Constantinople mint. mintmark CONOB.
DATE: 408 - 450 AD (this coin issued between 408 - 420 AD)
MINTMARK: COMOB (Constantinople, Turkey)
SIZE: 19.9mm diameter
WEIGHT: 3.77 grams
ATTRIBUTION: RIC X 202m Sear 21127
PROVENANCE: Formerly in a private collection, Cumbria.