This Constantinopolis commemorative has an unusual decorated shield...they are usually just plain. With the crescent in left field and small size it looks like RIC VIII Arles 16. Though the style is good, I believe this coin must be unofficial because the seller gives its weight and size as 1.6gm and 13mm. The weight is close, but I would expect to see at least 15mm for an official coin, but perhaps it is just a seriously undersized flan. So I am tentatively calling it unofficial until a closer examination.