Byzantine coins from that period are solidi which were first minted under the reign of the emperor Constantine I the Great (306-337). Solidi were minted very precisely and the weight of each coin was controlled. Their weight was equal to 4,54 g. Partial units – semis (1/2 solidus) and mainly triens (1/3 solidus, 1,52 g) – were also minted. The Byzantine solidus was a decisive monetary unit used in vast parts of Europe, northern Africa and Asia Minor. Its use as numerical unit dates back to the Middle Ages. On the territory of Great Moravia it was used as the foreign trade currency. Solidi served also as a model for the first coins of early medieval states.