Dirham - Ibrahim

Ibrahim ibn al-Mahdi seized the caliphate in Baghdad in 817 after the death of al-Amin's successor al-Ma'mun was falsely reported, ruling as an anti-caliph for roughly two years before al-Ma'mun's forces reclaimed the city. Coins struck in Ibrahim's name are accordingly rare — his mint output was geographically limited and his reign ended with his flight into hiding, where he remained concealed for nearly eight years before surrendering.

Album E225 designates this as an emission of his contested caliphate rather than a later issue, a distinction that matters considerably for attribution given how briefly the type was produced.