'Abbasid Caliphate. temp. Al-Mahdi. AH 158-169 / AD 775-785. Yahya b. Mikhnaq. AH 162-164 / AD 779-781. AR Hemidrachm (23.6mm, 1.92g, 9h). Tabaristan mint. Dated PYE 129 = AH 164 / AD 780/1. Obverse: Name of governor before bust. Reverse: Pellet above second 'T' of mint-name. Star to left and crescent to right of flames. Malek 89.2; Album 60 RR. EF. Rare.