The origin of the troy weight system is unknown, although the name probably comes from the
Champagne fairs at
Troyes, in northeastern France. English troy weights were nearly identical to the troy weight system of
Bremen. (The Bremen troy ounce had a mass of 480.8 British Imperial grains.) The British Imperial troy ounce (known more commonly simply as the imperial troy ounce) was based on, and virtually identical to, the pre-1824 British troy ounce and the pre-1707 English troy ounce. (1824 was the year the British Imperial system of weights and measures was adopted; 1707 was the year of the
Act of Union which created the
Kingdom of Great Britain.) Troy ounces have been used in England since the early 15th century, and the English troy ounce was officially adopted for coinage in 1527. Before that time, various sorts of troy ounces were in use on the continent. The troy ounce and grain were also part of the
apothecaries' system. This was long used in medicine, but has been largely replaced by the
metric system (milligrams). The only troy weight in widespread use is the British Imperial troy ounce and its American counterpart. Both are based on a grain of 0.06479891 gram (exact, by definition), with 480 grains to a troy ounce (compared with grains for an ounce avoirdupois). The British Empire abolished the 12-ounce troy pound in the 19th century. It has been retained, though rarely used, in the American system. Larger amounts of precious metals are conventionally counted in hundreds or thousands of troy ounces, or in kilograms. Troy ounces have been and are still often used in precious metal markets in countries that otherwise use
International System of Units (SI). However, the
People's Bank of China which had been using troy measurements in minting
Gold Pandas since 1982 from 2016 specifies Chinese bullion coins in an integer numbers of grams. ==Units of measurement==