Editing Troy weight (section)

==Units of measurement==
[[File:comparison of pounds.svg|thumb|400px|Chart comparing the mass (in grams) of tower, Troy, merchant, avoirdupois and London pounds. Each colored block represents one of that system's ounces (gold=Troy, blue= avoirdupois, purple=tower)]]

===Troy pound (lb t) <span class="anchor" id="Troy pound"></span>===
[[File:TroyPoundEngraving.jpg|thumb|The standard British troy pound manufactured in 1758; it bears the abbreviation<!--not a ligature, it is a bar to signify abbreviation (see [[bar (diacritic)]] --> {{char|[[℔]]}} ("pound") and the letter "T" for troy.]]
The troy pound (lb t) consists of twelve troy ounces<ref name="Perth Mint">{{cite web |title=Units of measure | publisher=[[Perth Mint]] |url=https://www.perthmint.com/education_uom.aspx |url-status=dead |archive-url=https://web.archive.org/web/20190607051942/https://www.perthmint.com/education_uom.aspx |archive-date=7 June 2019}}</ref> and thus is {{convert|5760|gr|g|abbr=off|sigfig=8|comma=gaps}}. (An avoirdupois pound is approximately 21.53% heavier at {{convert|7000|gr|g|abbr=off|sigfig=8|comma=gaps}}, and consists of sixteen avoirdupois ounces).

===Troy ounce (oz t) <span class="anchor" id="Troy ounce"></span>===
A troy ounce weighs 480 [[Grain (unit)|grains]].<ref name="Perth Mint" /> Since the implementation of the [[international yard and pound]] agreement of 1 July 1959, the grain measure is defined as precisely {{val|64.79891|u=[[milligram]]s}}.<ref name="NIST">National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds. [https://www.nist.gov/pml/wmd/pubs/upload/AppC-12-hb44-final.pdf "Appendix C – General Tables of Units of Measurement"] {{Webarchive|url=https://web.archive.org/web/20160617040949/http://www.nist.gov/pml/wmd/pubs/upload/AppC-12-hb44-final.pdf |date=2016-06-17 }} (PDF). [https://www.nist.gov/pml/wmd/pubs/h44-12.cfm ''Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices''] {{Webarchive|url=https://web.archive.org/web/20160823052024/http://www.nist.gov/pml/wmd/pubs/h44-12.cfm |date=2016-08-23 }}. NIST Handbook. '''44''' (2012 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology. [[International Standard Serial Number|ISSN]] [http://www.worldcat.org/issn/0271-4027 0271-4027] {{Webarchive|url=https://web.archive.org/web/20221225104227/https://www.worldcat.org/search?q=n2:0271-4027 |date=2022-12-25 }}. [[Online Computer Library Center|OCLC]] {{OCLC|58927093}}. Retrieved 30 June 2012.</ref>{{rp|C-19}}<ref name="nbs447">{{cite book |last=Judson |first=Lewis V. |title=Weights and Measures Standards of the United States: A brief history |url=https://www.nist.gov/pml/pubs/sp447/index.cfm |format=PDF |access-date=30 June 2012 |series=NBS Special Publication |volume=447 |date=March 1976 |orig-year=October 1963 |publisher=U.S. Department of Commerce, National Bureau of Standards |location=Washington, D.C. |oclc=610190761 |page=20 |chapter=8. Refinement of values for the yard and pound |chapter-url=http://physics.nist.gov/Pubs/SP447/sec08.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110603064530/https://www.nist.gov/pml/pubs/sp447/index.cfm |archive-date=3 June 2011 }}</ref> Thus one troy ounce = {{convert|1|ozt|gr|0|disp=out|abbr=off|comma=gaps}} × {{convert|1|gr|g|8|disp=out|abbr=off|comma=gaps}}/grain = {{convert|1|ozt|g|8|disp=out|abbr=off|comma=gaps}}. Since the ounce avoirdupois is defined as 437.5 grains, a troy ounce is exactly {{frac|480|437.5}} = {{frac|192|175}} 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&nbsp;g in EU directive 80/181/EEC.<ref name="80/181/EER">{{cite web | url=https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:01980L0181-20200613#tocId31 | title=Consolidated TEXT: 31980L0181 — EN — 13.06.2020 }}</ref>

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 grams. The divisions are identical to the tower system.<ref name="Kelly">{{cite book |last=Kelly |first=Patrick|title=Universal Cambist and Commercial Instructor |url=https://archive.org/details/universalcambist0001kell/page/n6/mode/1up |year=1821 |location=London |page=[https://archive.org/details/universalcambist0001kell/page/20/mode/1up 20]}}</ref>

===Pennyweight (dwt)===
The [[pennyweight]] symbol is ''dwt''. One pennyweight weighs 24 grains, and 20 pennyweights make one troy ounce.<ref name="Perth Mint" /> Because there were 12 troy ounces in the old troy pound, there would have been 240 pennyweights to the pound (mass){{snd}} just as there were 240 pennies in the [[Pound sterling#Anglo-Saxon, c 800 CE|original pound-sterling]]. However, prior to 1526, the English [[pound sterling]] was based on the [[tower pound]], which is {{frac|15|16}} of a troy pound. The ''d'' in ''dwt'' stands for ''[[denarius]]'', 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===
{{main|Grain (mass)}}

There is no specific 'troy grain'. All [[imperial unit|Imperial systems]] use the same measure of mass called a grain (historically of [[barley]]), each weighing {{frac|1|7000}} of an avoirdupois pound (and thus a little under 65 milligrams).{{Efn|Because an avoirdupois pound weighs 7000 grains and a pound is [[International Yard and Pound Agreement|legally defined]] as having a mass of exactly 0.45359237{{nbsp}}kg (453.59237 g, 453592.37 mg), one grain weighs 453592.37/7000{{nbsp}}mg (or nominally  64.79891{{nbsp}}mg  to seven [[significant figure]]s,  but this would be an example of [[false precision]].)}}

===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.<ref name="Britain)1891">{{cite book|publisher=Philological Society (Great Britain)|title=A new English dictionary on historical principles: founded mainly on the materials collected by the Philological Society|url=https://books.google.com/books?id=k2xXAAAAYAAJ&pg=PA675|year=1891|via=Clarendon Press|page=675}}</ref><ref name="Miege">{{cite book|last=Miege|first= Guy|title=The Present State of Great Britain and Ireland|url=https://books.google.com/books?id=BDs2AAAAMAAJ&pg=PA307|year=1738|publisher=J. Brotherton, A. Bettesworth and C. Hitch, G. Strahan, W. Mears, R. Ware, E. Symon, and J. Clark|page=307}}</ref>