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This is an ancient Roman gold solidus of emperor Gratian dating to struck at the Milan mint between 380 - 382 AD.
Obverse: D N GRATIA-NVS P F AVG, ""Our Lord Gratianus, the Devout, the Fortunate, the Majestic." Pearl-diademed, draped and cuirassed bust of Gratian facing right.
Reverse: VICTOR-IA AVGG, "Victory of the Augusts (emperors)" Two emperors nimbate, seated facing, together holding globe; behind and between them, the upper part of Victory with outspread wings. Below, on exergual line, palm branch; in exergue, COM*.
*The moneta comitatensis was a travelling mint attached to the imperial train wherever the emperor was situated. A special mintmark COM for comitatus (or COMT.M) Most coins signed by the comitatensian mint also bear a supplementary abbreviation referring to the name of the town where the coin was actually struck in this case in it was Mediolanum (Milan).
DATE: 367 - 383 (this coin minted in 380 - 382 AD)
MINTMARK: COM (Milan, Italy)
SIZE: 21mm diameter
WEIGHT: 4.39 grams
ATTRIBUTION: Toffanin 437; Depeyrot 1/1 C 38. RIC 5d (Mediolanum).
NGC Photo certificate grade VF; Strike: 5/5, Surface: 3/5. RARE