Grain (unit) weight) refers to those things measured by the lesser but quicker balances: the bismar or uncel, the Roman balance, and the steelyard. The original mercantile pound of 25 shillings or 15 (tower) ounces was displaced by variously the pound of the Hanseatic League (16 tower ounces) and by the pound of the then-important wool trade (16 ounces of 437 grains). A new pound of grains was inadvertently created as 16 troy ounces, referring to the new troy rather than the old troy. Eventually, the wool pound won out. The avoirdupois pound was defined in prototype, rated as to grains. In
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.