Editing Coin (section)

== Modern features ==
[[File:Contando Dinheiro (8228640).jpg|thumb|left|Coins can be stacked.]]
[[File:1884 trade dollar rev.jpg|thumb|upright|1884 [[Trade dollar (United States coin)|United States trade dollar]]]]
[[File:20franctrimetalrev.jpg|thumb|185px|French 1992 twenty Franc Tri-Metallic coin]]
[[File:Kingtutcoinobv without background.png|thumb|upright|Bimetallic Egyptian one pound coin featuring King Tutankhamen]]

The side of a coin carrying an image of a monarch, other authority (''see [[List of people on coins]]''), or a [[national emblem]] is called the ''[[obverse]]'' (colloquially, ''heads''); the other side, carrying various types of information, is called the ''[[Obverse and reverse|reverse]]'' (colloquially, ''tails''). The year of [[mint (coin)|minting]] is usually shown on the obverse, although some [[China|Chinese]] coins, most [[Canadian coinage|Canadian]] coins, the pre-2008 British [[Twenty pence (British decimal coin)|20p]] coin, the post-1999 American [[Quarter (United States coin)|quarter]], and all Japanese coins are exceptions.

The relation of the images on the obverse and reverse of a coin is the coin's orientation. If the image on the obverse of the coin is right side up and turning the coin left or right on its vertical axis reveals that the reverse of the coin is also right side up, then the coin is said to have [[medallic orientation]]—typical of the [[Euro]] and [[pound sterling]]; if, however, turning the coin left or right shows that the reverse image is upside down, then the coin is said to have [[coin orientation]], characteristic of the [[coins of the United States dollar]].

[[Bimetallic coins]] are sometimes used for higher values and for commemorative purposes. In the 1990s, France used a tri-metallic coin. Common circulating bimetallic examples include the [[1 euro coins|€1]], [[2 euro coins|€2]], [[One pound (British coin)|British £1]], [[Two pounds (British coin)|£2]] and [[Canadian 2 dollar coin|Canadian $2]] and several peso coins in Mexico.

The ''exergue'' is the space on a coin beneath the main design, often used to show the coin's date, although it is sometimes left blank or contains a [[mint mark]], [[privy mark]], or some other decorative or informative design feature. Many coins do not have an exergue at all, especially those with few or no legends, such as the Victorian bun penny.

[[File:RR5111-0173 3 рубля серебро 2008 аверс.gif|upright|thumb|3 [[Russian ruble|Rubles]] proof coin of Russia, minted in 2008]]
Not all coins are round; they come in a [[Coinage shapes|variety of shapes]]. The [[Fifty cent coin (Australian)|Australian 50-cent coin]], for example, has [[dodecagon|twelve flat sides]]. Some coins have wavy edges, e.g. the $2 and 20-cent coins of [[Coins of the Hong Kong dollar|Hong Kong]] and the 10-cent coins of Bahamas. Some are square-shaped, such as the 15-cent coin of the Bahamas and the 50-cent coin from Aruba. During the 1970s, [[Swaziland|Swazi]] coins were minted in several shapes, including squares, polygons, and wavy edged circles with 8 and 12 waves.

Historically, a considerable variety of [[coinage metals]] (including alloys) and other materials (e.g. [[porcelain]]) have been used to produce coins for circulation, collection, and metal investment: bullion coins often serve as more convenient stores of assured metal quantity and purity than other bullion.<ref>{{cite web |author=Clayton |first=Tony |title=Metals Used in Coins and Medals |url=http://www.coinsoftheuk.co.uk/pics/metal.html |access-date=2018-08-15 |publisher=coins-of-the-uk.co.uk}}</ref>

<gallery>
File:Israelwave.jpg|Scalloped coin of Israel
File:Belizeonecentwave.jpg|1996 one cent coin from Belize
File:Phil2pisodecrev.jpg|Decagonal two Piso Philippine coin 1990
</gallery>

Some other coins, like the British [[Twenty pence (British coin)|20]] and [[Fifty pence (British coin)|50 pence coins]] and the Canadian [[Loonie]], have an odd number of sides, with the edges rounded off. This way the coin has a [[Curve of constant width|constant diameter]], recognizable by [[vending machine]]s whichever direction it is inserted.

A triangular coin with a face value of [[Five pounds (British coin)|£5]] (produced to commemorate the 2007/2008 [[Tutankhamun]] exhibition at [[The O2 Arena]]) was commissioned by the [[Isle of Man]]: it became legal tender on 6 December 2007.<ref>It is unlikely to be spent as it costs 15[[Pound sterling|GBP]] to buy – article ''Pyramid coin a nightmare for pockets'', article by Gary</ref> Other triangular coins issued earlier include: [[Republic of Cabinda|Cabinda]] coin, [[Bermuda]] coin, 2 Dollar [[Cook Islands]] 1992 triangular coin, [[Uganda]] Millennium Coin and [[Poland|Polish]] Sterling-Silver 10-Zloty Coin.

Some medieval coins, called [[bracteate#High_medieval_bracteates|bracteate]]s, were so thin they were struck on only one side.

Many coins over the years have been manufactured with integrated holes such as Chinese "cash" coins, Japanese coins, Colonial French coins, etc. This may have been done to permit their being strung on cords, to facilitate storage and being carried. Nowadays, holes help to differentiate coins of similar size and metal, such as the Japanese [[50 yen coin|50 yen]] and [[100 yen coin]].

<gallery>
File:Frenchholeobv.jpg|1917 French coin with integrated hole
File:Chong Ning Tongbao 1.JPG|Chinese cash coin, 1102–1106
File:عملة فلسطينية معدنية.jpg|1941 British Palestine coin
File:50 Yen Rückseite.jpg|Modern-day Japanese 50-yen coin
File:1924 East African 1 cent coin reverse.jpg|1924 East African coin
</gallery>

[[File:Y2klibholoobv.jpg|thumb|185px|Holographic coin from Liberia features the [[Statue of Liberty]] (''Liberty Enlightening the World'')]]
The [[Royal Canadian Mint]] is now able to produce holographic-effect gold and silver coinage. However, this procedure is not limited to only bullion or commemorative coinage. The [[500 yen coin]] from Japan was subject to a massive amount of [[counterfeit]]ing. The Japanese government in response produced a circulatory coin with a holographic image.

The Royal Canadian Mint has also released several coins that are colored, the first of which was in commemoration of Remembrance Day. The subject was a colored poppy on the reverse of a 25-cent piece minted through a patented process.<ref>{{cite news|last1=Smith|first1=Marie-Danielle|title=Royal Canadian Mint sues Royal Australian Mint in row over poppy coin printing|url=https://nationalpost.com/news/canada/royal-canadian-mint-sues-royal-australian-mint-in-row-over-printing-of-red-poppies|access-date=18 January 2018|work=[[The National Post]]|date=18 January 2018}}</ref>

An example of non-metallic composite coins (sometimes incorrectly called plastic coins) was introduced into circulation in [[Transnistria]] on 22 August 2014. Most of these coins are also non-circular, with different shapes corresponding to different coin values.<ref>{{cite web |title=Composite coins |url=http://www.cbpmr.net/content.php?id=26&lang=en |url-status=live |archive-url=https://web.archive.org/web/20170704125452/http://www.cbpmr.net/content.php?id=26&lang=en |archive-date=4 July 2017 |access-date=29 January 2020 |website=Pridnestrovian Republican Bank}}</ref>

For a list of many pure metallic elements and their alloys which have been used in actual circulation coins and for trial experiments, see [[coinage metals]].<ref>{{cite web |author=Tony Clayton |url=http://www.tclayton.demon.co.uk/metal.html |title=Metals Used in Coins and Medals |publisher=Tclayton.demon.co.uk |access-date=2012-05-22 |url-status=dead |archive-url=https://web.archive.org/web/20100401072934/http://www.tclayton.demon.co.uk/Metal.html |archive-date=2010-04-01 }}</ref>