Facts concerning the Origin of the Troy Weight Standard – Robert Tye

A Troy pennyweight of 24 Troy grains historically derived from the half of an Islamic pre-existing bullion dirhem of 48 grains.  Developing that study of weight standards by a further study of coin weight, Skinner (1967) judged the derivation beyond doubt, after showing the early post reform Arabic dirhem “set the standard for the English Penny Sterling” (i.e. that the 22.5 grain sterling penny is intentionally a half of the 45 grain dirhem), which therefore “had a direct effect upon later English standards”.