By the way, about the 12 nummi coins that are ascribed to the Persian occupation of Alexandria, I just saw this interesting article 'Copper Coinage of Egypt in the Seventh Century' by Lidia Domaszewicz and Michael L. Bates. Full details: 'The Copper Coinage of Egypt in the Seventh Century,' in Fustat Finds. Beads, Coins, Medical Instruments, Textiles, and Other Artifacts from the Awad Collection (ed. Jere L. Bacharach. Cairo, American University in Cairo Press, 2002), pp. 88-111. It is on Academia.edu and might be behind a paywall. To cut things very short, Bates and Domaszewicz on p.100-102 of their article, fire some persuasive shots at the interpretation of the 12 nummi - frontal head with star and crescent - as Persian. They say it might be coinage possibly issued by Anastasius (491-518), a century earlier. I can't judge this and I don't know if this issue has been commented since. Published hoards or other archeological evidence may contain answers that I don't know of. But I think it might interest you.