The Byzantine Empire issued the gold solidus, or nomisma, used primarily for large transactions such as tax payments, and several denominations of copper coins, the money of daily business transactions. Mints in Antioch and Alexandria supplied the majority of the coinage circulated in the southern provinces. The newly established Arab government inherited an efficient monetary system and made few changes during its first decades. The earliest Islamic coins derive from Byzantine coinage, most frequently that of the early seventh century. The caliph ‘Abd al-Malik (r. 685–705) introduced several issues of distinctively Islamic coinage. Countermarked coins circulated widely during the Byzantine reoccupation of the region, 630–40, but their purpose is unclear.
Inscription: In Greek, on reverse: 40; below: workshop 4; left and right: year 20; in exergue: Con[stantinople]; countermarked with monogram for Heraclius
New York. The Metropolitan Museum of Art. "Byzantium and Islam: Age of Transition (7th–9th Century)," March 12, 2012–July 8, 2012.