501 Treasures of Byzantium: No.9 Gold hyperpyron of Alexius I, probably minted 1092-1118, Thessalonica.

It is an astonishing feat to imagine that the gold coin created by Constantine in the early fourth century, known as the solidus or nomisma, would retain its purity and value (4.5 grams of gold per coin) for over seven centuries. (Diocletian introduced the first slightly heavier prototype of the solidus in 301.) It was used so widespread throughout the empire that trade and savings prospered and it paid for important government institutions and projects. Unfortunately, early in the eleventh century it began to increasingly depreciate in value and purity, largely caused by a number of unwelcomed factors, such as inferior alloy coins, military disasters and civil war.

In its place Alexius I Komnenos, initiated a recovery plan for the ailing Byzantine currency during the first decade of his reign. Expect it wasn’t simply a reissue of old coinage, it was the minting of a totally new high-quality gold issue. The Hyperpyron came about because the Byzantine monetary system was inevitably in need of a serious overhaul. It appearance interestingly coincided with Alexis making his eldest son John his successor. How better to celebrate a coronation by issuing a new coin!

The hyperpyron (scyphate or concave in shape) was minted at the same standard weight, as the old solidus and was almost all completely pure gold at 201/2 carats, compared to the old solidus at 24. It too, however, suffered the same fate as all other previous gold coins and began a gradual slide into depreciation. By the fourteenth century, it had depreciated to half its original value. Eventually, the Byzantines love affair with gold coinage, was substituted in favour of Italian currency.