Pound (mass) for the weight of certain precious metals, especially in the trade; these are normally quoted just in ounces (e.g. "500 ounces") and, when the type of ounce is not explicitly stated, the troy system is assumed. Historically, the pound sterling was a Tower pound of silver. In 1528, the standard was changed to the Troy pound. The avoirdupois pound, also known as the wool pound, first came into general use c. 1300. It was initially equal to 6992 troy grains. The pound avoirdupois was divided into 16 ounces. During the reign of Queen Elizabeth, the avoirdupois pound was redefined as
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