A Pendant of the Byzantine's Constantine golden coin, 14k.

The Byzantine's Constantine golden coin was minted ad 324 or 325.

Size: Diameter= 2.7 cm. Diameter= 1 inch. 

At first, it was introduced as a replacement of the aureus, however, and the coin only entered widespread circulation under Constantine 1 after ad 312, when it permanently replaced the Aureus. 

Bezant was originally a relatively pure gold coin issued in the Late Roman Empire. Under Constantine, who introduced it on a wide scale, it had a weight of about 4.5 grams. It was largely replaced in Western Europe by Pepin the Short's currency reform, which introduced the silver-based pound/shilling/penny system, under which the shilling (Latin: solidus) functioned as a unit of account equivalent to 12 pence, eventually developing into the French sou. In Eastern Europe, the nomisma was gradually debased by the Byzantine emperors until it was abolished by Alexius I in 1092, who replaced it with the hyperpyron, which also came to be known as a "bezant". The Byzantine solidus also inspired the originally slightly less pure Arab dinar.