ABBASID CALIPHS, al-Ma'mun, 810-833 AD. AR Dirhem (2.90 gm; 25 mm). Obverse, Shahadah followed by name "al-Mashriq" (meaning "East"), mint: "Madinat al Samarqand", year 199 AH, reverse, shahadah for propohet Mohamad followed by title "Dhu'l-Ri'asatayn" (commander of two branches of government, civilian and military). Abul-Abbas al-Fadl ibn sahl Zadanfarrukh-e Sarakhsi, titled Dhu 'l-Ri'asatayn was the grand vizir of Khalif al-Ma'mun who managed the Abbasid empire for a brief period of time and before his assassination. He persuaded Ma'mun to select the 8th Shia Imam, Ali-Ibn Musa al-Reza as the crown prince and successor which Ma'mun did. However both Fadl and the Imam fell victim to the plots of courtiers whom feared the rise of Persian power replacing the Arab power within the Abbasid empire. This is one of the most popular of all Abbasid coins given this history. Choice UNC with some luster. Very rare.