Byzantine Empire was a continuation of the Roman Empire into its eastern part and was strongly Christian area. they considered themselves Roman but spoke Greek also.
The capital of Rome was transferred to Constantinople in 330AD .
The monetary system of the Byzantine Empire was created by Constantine the Great. He continued the reforms of Diocletian (284-305) and put an end to inflation, at least partially.
He created a system based on a gold coin, a solidus or solid (gold), made from pure gold (23 ½ k) with a weight of 4,4 gr. The solidus depicts the emperor’s portrait on one side and different scenes on the back, usually a scene with a Victory holding a cross.
Also, it had some small gold subdivisions, a semissis or half and tremissis or third.
The solidus was marked with the letters OB, meaning, if it is read as letters, obryzum “pure gold” or if it is read as a numeral, “72”, from one pound of gold, the emperor minted 72 gold coins.
This coin was produced in the imperial mint of Constantinopol and thus the marking is CONOB. Moreover, coins like this were minted in Thessalonik, Antiochia, Cyzic and so on.
This gold coin was meant to be used on a large scale transaction. Gold was a rare metal. It was used for paying the army, for gifts to the high rank functionaries of the empire or in the great affaires.
The solidus kept its value and weight until the XI century. Only in the IX century the title began to become a little bit low, around 20-22 k.
Also, a VI century situation must be mentioned, when the emperor minted some particular gold coins. Instead of 24 siliqua or 4,4 grams, they had a weight of 4,0-4,2 gr., that is 20-23 siliqua. Of course, you can hardly feel the difference between a 4,2 gr. coin and a 4,4 gr. coin but for the imperial house, that minted thousands of coins like these, it meant a big economy of gold. For example, at a mintage of 10000 coins, the emperor saved around 2 kg of gold. These coins were minted with the same dies as the normal solidus. Only some particular marks, like OBXX or +OB+ or something similar, can make the difference.
These light coins were meant to be used in external exchanges with the barbarian population.
The silver was a rare coin in the Byzantine society. Constantine minted a coin named siliqua, around 2,4 gr. of silver and 1/24 from a solidus (the name siliqua was used for a unit measure for gold: the silver coin corresponded to the weight of silver for a gold siliqua). Also a coin named miliarense was minted, with a weight of around 4 gr. Its name came from “one thousand” meaning that 1000 silver coins like this values one pound of gold.
These silver coins were minted only until 400, when they were withdrawn from circulation and the minting stopped.
The bronze coinage was the weak part of this system. Originally one follies had a weight of 12 gr. (304), it dropped to 8 (307) and 6,5 (309). In 313 it has a weight of only 3 gr. and in 337, the year of Constantine’s death, only 1,5 gr.
During the IV century, different attempts were made and emperors such as Constantius II or Julian (361-363) tried to solve the problems but failed. In 400 AD, the coin, named nummus had a weight of 1 gr. and used in local exchanges, at a rate of 1/7200 for a gold coin.
In 400 AD, the monetary situation of the empire was reduced to one gold coin, with 2 subdivisions, for universal trade, and a bronze one, the nummus, for local trade. These lasted until 498. For the period 498-1453, the monetary history of the Byzantine empire is divided in 5 stages.
The first starts with the reign of Anastasius and his reforms. It started in 498 and ended around 750 AD. It is characterized by 3 gold coins, 5 copper coins and one silver coin, the hexagram .
The second period of time starts around 750 and ends after 1081, and it is characterized by the simplification of the system.
The third period of time starts with the reign of Alexius Comnenus (1081-1118). In 1091-2 he introduced a gold coin, the hyperperon or “purified by fire”, and can be traced easily because of the concave shape, not flat as the previous ones. The old tremissis was replaced by a gold coin but with a low finesse of gold. The silver coinage was abandoned and a billon one was introduced, with only 6-10 % silver. This coin was named trachea and also can be recognized by the concave shape. And finally a new copper coin, named tetrateron, was introduced, with a subdivision sometimes made from lead. This system collapsed around 1204, after the fall of the Constantinopol in front of the IVth Crusade.
The fourth period of time, lasting from soon after 1300 to 1350 saw the introduction of a silver coin similar to the ducat of Venice, coin named basilicon , or the king’s coins and of a small copper coin, known as the assarion.
The fifth period of time starts from around 1350 to the fall of the empire, in 1453, and it is characterized by the complete and total disappearance of gold coins and the return of the silver and copper ones. The empire was too poor to have any gold coins.