Elmacin, who dates the first coinage A. H. 76, A.D. 695, five or six years later than the Greek historians, has compared the weight of the best or common gold dinar to the drachm or dirhem of Egypt (p. 77), which may be equal to two pennies (48 grains) of our Troy weight (Hooper's Inquiry into Ancient Measures, p. 24 - 36), and equivalent to eight shillings of our sterling money. From the same Elmacin and the Arabian physicians, some dinars as high as two dirhems, as low as half a dirhem, may be deduced. The piece of silver was the dirhem, both in value and weight; but an old, though fair coin, struck at Waset, A. H. 88, and preserved in the Bodleian library, wants four grains of the Cairo standard (see the Modern Universal History, tom. i. p. 548 of the French translation.).
Note by Rev. H.H. Milman written 1782, revised 1845
Up to this time the Arabs had used the Roman or the Persian coins or had minted others which resembled them. Nevertheless, it has been admitted of late years, that the Arabians, before this epoch, had caused coin to be minted, on which, preserving the Roman or the Persian dies, they added Arabian names or inscriptions. Some of these exist in different collections. We learn from Makrizi, an Arabian author of great learning and judgment, that in the year 18 of the Hegira, under the caliphate of Omar, the Arabs had coined money of this description. The same author informs us that the caliph Abdalmalek caused coins to be struck representing himself with a sword by his side. These types, so contrary to the notions of the Arabs, were disapproved by the most influential persons of the time, and the caliph substituted for them, after the year 76 of the Hegira, the Mahometan coins with which we are acquainted. Consult, on the question of Arabic numismatics, the works of Adler, of Fraehn, of Castiglione, and of Marsden, who have treated at length this interesting point of historic antiquities. See, also, in the Journal Asiatique, tom. ii. p. 257, et seq., a paper of M. Silvestre de Sacy, entitled Des Monnaies des Khalifes avant l'An 75 de l'Hegire. See, also the translation of a German paper on the Arabic medals of the Chosroes, by M. Fraehn. in the same Journal Asiatique tom. iv. p. 331 - 347. St. Martin, vol. xii. p. 19