The Abbasid Caliphs were the holders of the Islamic title Caliph who was a member of the Abbasid dynasty. It is a branch of the Quraysh tribe descended from the uncle of the Islamic prophet Muhammad, al-Abbas ibn Abd al-Muttalib.
Al Mansur was the second Abbasid Caliph reigning from 136 to 158 AH. He was regarded as a real founder of the Abbasid Caliphate. He is also known for founding the round city of Madinat al-Salam which became the core of the imperial capital Baghdad.
This silver Dirham issued in the reign of Al Mansur from Ifriqiya mint in 145 AH. This coin bears the traditional formula on its obverse, the Kalima: “There is no God except Allah he has no Partner”. The reverse has the short legend "Mohammed is the Prophet of Allah."
Image Source: Stephen Album Rare Coins