ABBASID: 'Ubayd Allah, 788-790, AR dirham (2.90g), Arminiya, AH175, A-219G, Vardanyan-37, with the reverse legend mimma amara bihi al-amir / 'ubayd Allah bin / amir al-mu'minin and no other names or titles, choice VF to EF, RR. There is no clear evidence that 'Ubayd Allah (b. al-Mahdi) ever claimed to be heir-apparent to the caliphate, as inscribed on this coin.
Estimate: $300-400