ISLAMIC, 'Abbasid Caliphate. temp. Al-Mahdi, AH 158-169 / AD 775-785. Hemidrachm (Silver, 22 mm, 1.99 g, 6 h), citing the governor of Tabaristan, Umar ibn al-'Ala (AH 154-164 = AD 771-780), Tabaristan, PYE 128 = AH 163 = 779/80. Crowned and draped Sasanian-style bust to right; behind head, AFZUT GDH ('may his kingship increase' in Pahlawi); before head, 'AWMR' in Pahlawi; in outer margin, APD / NWKW ('excellent' and 'good' in Pahlawi. Rev. Sasanian fire altar set on three steps, flanked by two attending priests (mabedh) standing facing; to left, date; to right, mint TPURSTAN ('Tabaristan' in Pahlawi). Album 55. SICA I, 416. Walker, Arab-Sassanian, 271. Minor marks, otherwise, extremely fine.