A 9th-century Coin

This coin was minted by Maʾmun after the fourth fitna. Note the ʿAlid content.

Obverse: In field: “no deity other than the One God, He has no associate, the east”; Inner margin: “in the name of God this dirham was struck in Marw the year two and two hundred”; Outer margin: “the command is God’s, past and future, and on that day the faithful will rejoice in the victory granted by God.” [Surah 30: 4-5].

Reverse: In field : “for God, Muhammad is the messenger of God, al-Ma’mun, God’s caliph, among those things ordered by the Prince al-Rida, the heir to the Muslims, ‘Ali bin Musa’ bin ‘Ali bin Abi Talib, possessor of the two authorities”; In margin:  “Muhammad is the messenger of God, who sent him with guidance and the religion of truth that he might make it supreme over all other religions even though the polytheists may detest it” [9: 33]

A 9th-century Description

This passage is from Yaʿqubi, a historian and geographer who wrote in Arabic in the 9th century.

During al-Maʾmūn’s reign, al-Muʿtaṣim would send me to Nūḥ ibn Asad in Samarqand to purchase Turks. Each year I would bring him a certain number such that, during the reign of al-Maʾmūn, he had accumulated some three thousand of the slave recruits. When he assumed the office of caliph, al-Muʿtaṣim pressed ahead eagerly with this practice. He purchased slaves in Baghdad which he found in the possession of the citizenry. He bought a number in Baghdad all at once, among them Ashinās, who was then the property of Nuʿaym ibn Khāzim Abī Hārūn ibn Nuʿaym; Ītākh, then the property of Sallām ibn al-Abrash; Waṣīf, an armorer and the property of the Nuʿaym family; and Sīmā al-Dimashqī, the property of Dhū al-riʾasatayn al-Faḍl ibn Sahl.

Source, p. 17.

A 13th-century Depiction

This image shows Maʾmun on the left, receiving John the Grammarian as an envoy from the Byzantine court in 829. On the right is the Byzantine emperor Theophilos. This is from a 13th-century manuscript of an 11th-century Byzantine historian named Skylitzes, writing in Greek. The manuscript has some really amazing images, which you can find here.

This image is from the same manuscript, but shows Maʾmun writing to the Byzantine emperor.