The downfall of the Umaiyad and the rise of the ‘Abbāsid Caliphate, the central protagonist in which was the formidable Abū Muslim, is one of the most fascinating periods in Islamic History. Numismatic research is gradually revealing more and more vestiges of these troublous times. Recently in the JRAS. (July, 1932) Mr. Rhuvon Guest published a copper coin of Abū Muslim, now in the ‘Irāḳ Museum, which had been unearthed during irrigation work on the lesser Zāb, and which provided interesting corroborative evidence of the statements of the early Arab chroniclers. In a similar way I propose to draw attention to two copper coins in the British Museum, until now unpublished, which not only throw some light on the family relationship of Abū Muslim and his provincial politics, but moreover preserve for us a variety of coin legend which has hitherto been unrecorded and is perhaps unique in Muslim numismatics (Plate I).