Apothecaries' system the Roman weight system. An apothecaries' pound normally consisted of 12 ounces. (In France this was changed to 16 ounces, and in Spain the customary unit was the "marco", a mark of 8 ounces.) In the south of Europe and in France, the scruple was generally divided into 24 grains, so that one ounce consisted of 576 grains. Nevertheless, the subdivision of an ounce was somewhat more uniform than that of a pound, and a common feature of all variants is that 12 ounces are roughly 100 drachms (96–128 drachms) and a grain is roughly the weight of a physical
Pound (mass) 6750 troy grains, or 9600 Tower grains, derives from this pound, as 25 shilling-weights or 15 Tower ounces, for general commercial use. Multiple pounds based on the same ounce were quite common. In much of Europe, the apothecaries' and commercial pounds were different numbers of the same ounce. The Tower system was referenced to a standard prototype found in the Tower of London and ran concurrently with the avoirdupois and troy systems until the reign of Henry VIII, when a royal proclamation dated 1526 required that the troy pound to be used for mint purposes instead of the Tower pound.