Watch List notes:

ISLAMIC, 'Abbasid Caliphate. al-Ma'mun. AH 199-218 / AD 813-833. AR Dirham (27mm, 2.87 g, 10h). Citing 'Ali ibn Musa al-Rida as heir and Dhu'-l Ri'asatayn. Madinat Isbahan mint. Dated AH 204 (AD 819/20). Album 224; ICV 391. VF, toned. Rare.