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Troy weight is a system of
unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatrical presentation Music * ''Unit'' (a ...
s of
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different ele ...
that originated in 15th-century England, and is primarily used in the
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lu ...
s industry. The troy weight units are the
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
, the pennyweight (24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of the
avoirdupois system The avoirdupois system (; abbreviated avdp.) is a measurement system of weights that uses pounds and ounces as units. It was first commonly used in the 13th century AD and was updated in 1959. In 1959, by international agreement, the definiti ...
, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. One troy ounce (oz t) equals exactly 31.1034768 grams.


Etymology

Troy weight probably takes its name from the French market town of
Troyes Troyes () is a commune and the capital of the department of Aube in the Grand Est region of north-central France. It is located on the Seine river about south-east of Paris. Troyes is situated within the Champagne wine region and is near ...
where English merchants traded at least as early as the early 9th century. The name ''troy'' is first attested in 1390, describing the weight of a platter, in an account of the travels in Europe of the Earl of Derby. Charles Moore Watson (1844–1916) proposes an alternative etymology: ''The Assize of Weights and Measures'' (also known as ), one of the statutes of uncertain date from the reign of either Henry III or
Edward I Edward I (17/18 June 1239 – 7 July 1307), also known as Edward Longshanks and the Hammer of the Scots, was King of England and Lord of Ireland from 1272 to 1307. Concurrently, he ruled the duchies of Aquitaine and Gascony as a vas ...
, thus before 1307, specifies ""—which the Public Record Commissioners translate as "troy weight". The word refers to markets. Watson finds the dialect word ''troi'', meaning a balance in Wright's ''The English Dialect Dictionary''. Troy weight referred to the tower system; the earliest reference to the modern troy weights is in 1414.


History

Many aspects of the troy weight system were indirectly derived from the Roman monetary system. Before they used coins, early Romans used bronze bars of varying weights as currency. An ("heavy bronze") weighed one pound. One twelfth of an was called an , or in English, an "ounce". Before the adoption of the metric system, many systems of troy weights were in use in various parts of Europe, among them Holland troy, Paris troy, etc. Their values varied from one another by up to several percentage points. Troy weights were first used in England in the 15th century, and were made official for gold and silver in 1527. The British Imperial system of weights and measures (also known as
Imperial units The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed th ...
) was established in 1824, prior to which the troy weight system was a subset of pre-Imperial English units. The troy ounce in use today is essentially the same as the British Imperial troy ounce (1824–1971), adopted as an official weight standard for
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
coinage by Act of Congress on May 19, 1828. The British Imperial troy ounce (known more commonly simply as the imperial troy ounce) was based on, and virtually identical with, 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 The Kingdom of Great Britain (officially Great Britain) was a sovereign country in Western Europe from 1 May 1707 to the end of 31 December 1800. The state was created by the 1706 Treaty of Union and ratified by the Acts of Union 1707, wh ...
.) Troy ounces have been used in England since about 1400 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 The apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists."Medicinal-Gewicht, Apothek ...
. This was long used in medicine, but has now been largely replaced by the
metric system The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Intern ...
(milligrams). The only troy weight in widespread use today is the British Imperial troy ounce and its American counterpart. Both are currently 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, though it has been retained (although rarely used) in the American system. Larger amounts of precious metals are conventionally counted in hundreds or thousands of troy ounces (or in kilograms).


Origin

The origin of the troy weight system is unknown. Although the name probably comes from the
Champagne fairs The Champagne fairs were an annual cycle of trade fairs which flourished in different towns of the County of Champagne in Northeastern France in the 12th and 13th centuries, originating in local agricultural and stock fairs. Each fair lasted about ...
at
Troyes Troyes () is a commune and the capital of the department of Aube in the Grand Est region of north-central France. It is located on the Seine river about south-east of Paris. Troyes is situated within the Champagne wine region and is near ...
, in northeastern France, the units themselves may be of more northern origin. English troy weights were nearly identical to the troy weight system of
Bremen Bremen ( Low German also: ''Breem'' or ''Bräm''), officially the City Municipality of Bremen (german: Stadtgemeinde Bremen, ), is the capital of the German state Free Hanseatic City of Bremen (''Freie Hansestadt Bremen''), a two-city-state cons ...
. (The Bremen troy ounce had a mass of 480.8 British Imperial grains.) An alternative suggestion is that the weights come from the Muslim domains by way of the Gold Dirhem (47.966 British Imperial grains), in the manner that King Offa's weights were derived from the silver Dirhem (about 45.0 British grains). According to Watson, troy relates to a dialect word troi (balance). Then troy weight is a style of weighing, like auncel or bismar weights, or other kindred methods. The troy weight then refers to weighing of small precious or potent goods, such as
bullion Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes fro ...
and medicines.


Use in other countries

Troy ounces have been and are still often used in precious metal markets in countries that otherwise use
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
(SI), except in
East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea ...
. However, the People's Bank of China has previously used troy measurements in minting Gold Pandas beginning in 1982; since 2016, the use of troy ounces has been replaced by integer numbers of grams.


Units of measurement


Troy pound (lb t)

The troy pound (lb t) consists of twelve troy ounces and thus is . (An avoirdupois pound is approximately 21.53% heavier at 7000 grains, and consists of sixteen avoirdupois ounces).


Troy ounce (oz t)

A troy ounce weighs 480
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s. Since the implementation of the international yard and pound agreement of 1 July 1959, the grain measure is defined as precisely .National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds
"Appendix C – General Tables of Units of Measurement"
(PDF)
''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices''
. NIST Handbook. 44 (2012 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology.
ISSN An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...
br>0271-4027
.
OCLC OCLC, Inc., doing business as OCLC, See also: is an American nonprofit cooperative organization "that provides shared technology services, original research, and community programs for its membership and the library community at large". It wa ...
. Retrieved 30 June 2012.
Thus one troy ounce = × /grain = . Since the ounce avoirdupois is defined as 437.5 grains, a troy ounce is exactly = or about 1.09714 ounces avoirdupois or about 9.7% more. The Troy ounce for trading precious metals is considered to be sufficiently approximated by 31.10 g in EU directive 80/181/EEC


Pennyweight (dwt)

The pennyweight symbol is ''dwt''. One pennyweight weighs 24
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s and 20 pennyweights make one troy ounce. Because there were 12 troy ounces in the old troy pound, there would have been 240 pennyweights to the pound (mass) just as there were 240 pennies in the original pound-sterling. However, prior to 1526, English
pound sterling Sterling (abbreviation: stg; Other spelling styles, such as STG and Stg, are also seen. ISO code: GBP) is the currency of the United Kingdom and nine of its associated territories. The pound ( sign: £) is the main unit of sterling, and ...
was based on the tower pound, which is of a troy pound. The ''d'' in ''dwt'' stands for ''
denarius The denarius (, dēnāriī ) was the standard Roman silver coin from its introduction in the Second Punic War to the reign of Gordian III (AD 238–244), when it was gradually replaced by the antoninianus. It continued to be minted in very ...
'', the ancient Roman coin that equates loosely to a penny. The symbol ''d'' for penny can be recognized in the form of British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols ''£'', ''s'', and ''d'', respectively.


Troy grain

There is no specific 'troy grain'. All Imperial systems use the same measure of mass called a grain (historically of
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
), weighing exactly 64.79891 milligrams.


Mint masses

Mint masses, also known as ''moneyers' masses'' were legalized by Act of Parliament dated 17 July 1649 entitled ''An Act touching the monies and coins of England''. A grain is 20 mites, a mite is 24 droits, a droit is 20 perits, a perit is 24 blanks.


Scottish system

In Scotland, the Incorporation of Goldsmiths of the City of Edinburgh used a system in multiples of sixteen. (''See Assay-Master's Accounts, 1681–1702, on loan from the Incorporation to the National Archives of Scotland''.) There were 16 drops to the troy ounce, 16 ounces to the Scottish troy pound, and 16 pounds to the stone. The Scots had several other ways of measuring precious metals and gems, but this was the common usage for gold and silver. The Scottish pound was 7,716 grains, but after the union of Scotland with England, was reduced to 7,680 grains. This divides to 16 ounces, each of 16 drops, each of 30 grains. The reduction made the ounce and grain equal in mass to the English standard.


Dutch system

The Dutch troy system is based on a mark of 8 ounces, the ounce of 20 engels (pennyweights), the Engel of 32 as. The mark was rated as 3,798 troy grains or 246.084 grammes. The divisions are identical to the tower system.


Conversions

The troy system was used in the
apothecaries' system The apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists."Medicinal-Gewicht, Apothek ...
, but with different further subdivisions.


Relationship to British coinage

King
Offa Offa (died 29 July 796 AD) was King of Mercia, a kingdom of Anglo-Saxon England, from 757 until his death. The son of Thingfrith and a descendant of Eowa, Offa came to the throne after a period of civil war following the assassination of Æth ...
's 8th century currency reform replaced the
sceat A ( ; ang, sceatt , ) was a small, thick silver coin minted in England, Frisia, and Jutland during the Anglo-Saxon period that normally weighed 0.8–1.3 grams. History Its name derives from Old English ', meaning "wealth", "money", and "co ...
with the
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
penny A penny is a coin ( pennies) or a unit of currency (pl. pence) in various countries. Borrowed from the Carolingian denarius (hence its former abbreviation d.), it is usually the smallest denomination within a currency system. Presently, it is t ...
. This coin was derived from half of a silver dirhem. The masses were then derived by a count of coins, by a mix of
Charlemagne Charlemagne ( , ) or Charles the Great ( la, Carolus Magnus; german: Karl der Große; 2 April 747 – 28 January 814), a member of the Carolingian dynasty, was King of the Franks from 768, King of the Lombards from 774, and the first E ...
and
Roman Roman or Romans most often refers to: * Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lett ...
systems. An ounce was set as twenty pence, and a pound to twelve ounces or 240 silver pence. In practice, the weights of the coins was not consistent and 240 of them seldom added up to a full pound; there were no shilling or pound coins and the pound as used only as an accounting convenience. Later kings debased the coin, both in weight and fineness. The original pound divided was the tower pound of 5,400
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s, but a later pound of 5,760 grains displaced it. Where once 240 pence made a tower pound (and 256 make a troy pound), by the time of the United Kingdom Weights and Measures Act of 1824, a troy pound gives 792 silver pence, still minted as such as
Maundy Money Royal Maundy is a religious service in the Church of England held on Maundy Thursday, the day before Good Friday. At the service, the British monarch or a royal official ceremonially distributes small silver coins known as "Maundy money" (lega ...
.


See also

*
Bullion Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes fro ...
* Bullion coin * Carat (unit) *
Conversion of units Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects. Overview The process ...
* English units * Fluid ounce * Grain (unit) *
Imperial units The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed th ...
* Mark (weight) *
Tola (unit) The tola ( hi, तोला; ur, تولا ''tolā'') also transliterated as tolah or tole, is a traditional Ancient Indian and South Asian unit of mass, now standardised as 180 grains () or exactly 3/8  troy ounce. It was the base ...
*
United States customary units United States customary units form a system of measurement units commonly used in the United States and U.S. territories since being standardized and adopted in 1832. The United States customary system (USCS or USC) developed from English uni ...


Explanatory notes


References

{{Systems of measurement Precious metals Systems of units Units of mass Customary units of measurement in the United States