ISLAMIC, 'Abbasid Caliphate. Al-Mahdi, AH 158-169 / AD 775-785. Dirham (Silver, 24 mm, 2.85 g, 4 h), citing al-Mahdi as 'al-Khalifa', Qasr al-Salam, AH 168 = AD 785/6. SICA III, 1153. Rare. Very fine.
From a Swiss collection of Umayyad and Abbasid coins, assembled in the 1970-1980s (with original flip with S. Album's description).
The interesting mint Qasr al-Salam ('The Palace of Peace' in Kufic) was only active in the years AH 167-169. It was a located in a palace built by al-Mahdi near Madinat al-Salam, allegedly for the enormous sum of 50 Million Dirhams.