After the fall of the Western Roman Empire, two types of coins were typically used in the Eastern Roman Empire: a gold coin and a bronze coin. The golden coin was a gold solidus, while bronze was used for several clearly valued coins. As the empire came close to its end, new currency was only issued in silver and copper. The Byzantine coinage remained its prestige until the near end of the empire and it inspired a lot of European rulers. When rulers throughout Europe began issuing their own currency, they normally placed their own portrait on the obverse.
During the early days of the Byzantine Empire, the coins followed the Roman tradition. On the obverse side of the coin you would find the head of the emperor, while the reverse side was adorned with a Christian symbol, e.g. a cross or an angel. The gold coins issued by Justinian II broke this tradition by placing a bust of Jesus on the obverse side instead of the emperor and let a full-length portrait of the emperor decorate the reverse side.
During the 10th century, coins decorated with “anonymous folles” instead of a portrait of the emperor began to appear. Such a coin had a bust of Jesus on the obverse side and an inscription on the reverse side. The inscription read “XRISTUS/bASILEU/bASILE” which means “Christ, King of Kings”.