This is a Byzantine Gold Coin featuring Justin I AV Tremissis. Constantinople. It dates back to AD 492-518
Obverse description: D N IVSTINVS P P AVG, pearl-diademed, draped, and cuirassed bust right.
Reverse Description: VICTORIA AVGVSTORVM, Victory advancing right, head left, holding wreath in right hand and globus cruciger in left; star in right field, CONOB in exergue.
Age: 492-518 AD