Watch List notes:

ABBASID: al-Ma'mun, 810-833, AR dirham (2.87g), Isbahan, AH204, A-224, letter "S" below the reverse field, VF, R. 'Ali b. Musa al-Rida, Imam of the Shi'ite faction, was named heir to the caliphate as part of a failed attempt to reconcile the Sunni and Shi'ite branches of Islam. Unfortunately, al-Rida died in AH203, and it is believed that the posthumous issues of AH204-205 still citing al-Rida may have been produced in hopes of finding an alternative means of reuniting the Sunnis and Shi'ites.

Estimate: 400-500 USD