Coin Theodosius II.

The ancient Roman Empire was divided into two halves after the death of Emperor Theodosius I (ruling years 379 – 395) in 395 AD under his two sons Honorius and Arcadius. The Western Roman Empire and the Eastern Roman Empire were established. The western half perished in 476 due to the deposition of the last emperor Romulus Augustus by the Germanic tribes. The eastern part of the empire, however, remained until the 15th century and is now called the Byzantine Empire. This name comes from the original name of the capital Byzantium, which was later renamed Constantinople, today’s Istanbul, by the Roman Emperor Constantine the Great.
The Byzantine coins from the Eastern Roman Empire consisted mainly of the golden solidus and a variety of bronze coins. In 498, the Byzantine emperor Anastasius had reformed the coinage. The denominations were adjusted and the values M=40, K=20, I=10 and E=5 were stamped on the reverse, the obverse was given a stylized portrait of the emperor. Later, also the shapes were changed. 

Excluded from the reform, however, was the solidus (fixed reliable aureus), which remained the standard coin for international trade until the 11th century and thus circulated for more than a millennium. The solidus is also considered the model for the Islamic dinar and for Venetian and northern Italian coinage. It was the “reserve currency” for all of Europe and the entire Mediterranean region until the beginning of the 12th century and is referred to as the euro of the Middle Ages. The solidus shown in the illustration depicts the emperor on obverse with a helmeted armored bust with the titulature D N THEODOSIVS P F AVG (Our Lord Theodosius Pious and Happy August) and on reverse two enthroned emperors with circumscription SALVS REIPVBLICAE.