Copying follis of Constans II. Constans standing facing, traces of Greek letters // M (for "40 nummi"), dashes around, mintmark below. 21mm, 4.02 grams. Uncertain mint in the Middle East, minted c.635-670. 

From an old US collection, with the original collection ticket.

These coins are the earliest coins of the first Islamic Caliphate - after conquering the Byzantine Middle East, they issued coins in the corrupted style of Byzantine folli (especially of Constans II). These circulates for about a few decades, until the end of the 7th century.