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) and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or force. The libra (Latin for "scales / balance") is an ancient Roman unit of mass that was equivalent to approximately 328.9 grams. It was divided into 12 "unciae" (singular: "uncia"), or ounces. The "libra" is the origin of the abbreviation for pound, "lb". A number of different definitions of the pound have historically been used in Britain. Amongst these were the avoirdupois pound and the obsolete Tower, merchant's and London pounds. Troy pounds and ounces remain in use only