ISLAMIC, 'Abbasid Caliphate. temp. Al-Mahdi, AH 158-169 / AD 775-785. Hemidrachm (Silver, 25 mm, 1.93 g, 9 h), citing the governor of Tabaristan, Yahya ibn Mikhnaq (PYE 128-130 = AH 162-164 = AD 779-781), Tabaristan, PYE 129 = AH 164 = 780/1. Crowned and draped Sasanian-style bust to right; behind head, AFZUT GDH ('may his kingship increase' in Pahlawi); before head, 'Yahya' in Kufic; in outer margin, APD / NWKW ('excellent' and 'good' in Pahlawi) and floral ornaments. Rev. Sasanian fire altar set on three steps, flanked by two attendants standing facing; to left, date; to right, mint TPURSTAN ('Tabaristan' in Pahlawi). Album 60. SICA I, 418. Walker, Arab-Sassanian, p. 142, U.4. Rare. Extremely fine.