Watch List notes:

ABBASID: al-Ma'mun, 810-833, AR dirham (2.55g), Nishapur, AH203, A-224, citing 'Ali b. Musa al-Rida, recognized as heir by al-Ma'mun, representing al-Ma'mun's attempt to establish peace and cooperation between the Sunni and Shi'a branches of Islam; also citing the vizier Dhu'l-Ri'asatayn; one of the rare mints for this type, VF to EF, RR.

Estimate: 700-900 USD