At the beginning of his caliphate Hârûn ar-Rashîd introduced a reform by which the gold coinage, which may have been struck in several mints already during his fathers caliphate, became discernable through the addition of governors names. The only Muhammad with the position of a provincial governor in 171 H./787-788 AD was, according to Ibn al-Athîr, al-Kâmil, Beirut ed., vol VII p. 109 the Abbâsid Muhammad ibn Sulaymân ibn Alî, governor of the provinces around the gulf al-Basra, Bahrayn, al-Yamâma, Umân, al-Ahwâz and Fârs, of which al-Basra and al-Yamâma had mints at the period. A first specimen of this type was found 1997 for the Tübingen collection.