Close-up of some of the coins from the hoard of 264 found in a seventh century building in Jerusalem.
Heraclius reigned 610 to 641, and these are dated to the earlier part of his reign.
Heraclius is of course the Emperor that lost Jerusalem. Twice. To the Persians in 614, then to the Muslim Caliph in 638.
That's what makes the coins of Heraclius interesting - they were the Byzantine coins in circulation during and immediately after the life of Mohammed (d. 632), and were highly influential on the iconography of early Islamic coins.
I think claims that Mohammed was depicted on early Islamic coins in immitation of the Emperor on Byzantine ones is dubious at best. But if you look at the last coin here, of 'Abd al-Malik (AD 685-705) it is clear how the cross on one side of Byzantine coins was adapted.