What are KM Numbers?

Mauritius 1992 5 rupees, KM# 56

Once you start to explore the world of foreign coin collecting, you'll inevitably run across KM numbers (frequently abbreviated "KM#"). Collecting sites like Numista and World Coin Gallery list them prominently in their search results. eBay auctions for individual foreign coins frequently contain them. NGC's World Coin Price Guide includes them in its results. And if you ever tried to trade coins with someone with more collecting experience, they probably asked for, or gave, a KM number when describing a coin.

KM numbers are a numbering system for world coins created by the authors of the Standard Catalog of World Coins - Chester Krause ("K") and Clifford Mishler ("M") - which was first printed in 1972. The authors very astutely realized that it would make it easier for collectors to use their reference guide, and to be able to discuss specific coins, if there was a shorthand way of identifying a specific coin (instead of saying "The second type of the India 25 paise coin from 1967").

In the Standard Catalog, each country's coins are given a number (starting at 1 and counting up). KM numbers are generally assigned from oldest to newest, then from smallest to largest denomination. For example, in Mauritania the KM numbers look like this (ordered by KM number):

• 1/5 Ouguiya (1973): KM# 1
• 1 Ouguiya (1973): KM# 2
• 5 Ouguiya (1973-): KM# 3
• 10 Ouguiya (1973-): KM# 4
• 20 Ouguiya (1973-): KM# 5
• 1 Ouguiya (1974-): KM# 6

Notice that for the coins starting in 1973, the KM numbers follow the denominations - 1/5, 1, 5, 10, 20. Then in 1974, the 1 Ouguiya changed its design slightly and was given a new number (#6).

When a coin gets a new design (even a slight change), it usually is given a new number. In Great Britain, the pound coin cycles through different reverse designs to signify the 4 members of the United Kingdom (Great Britain, Scotland, Northern Ireland, and Wales). Each of these reverse designs is given its own KM number. Sometimes, a small design change receives a decimal-point number ("214.2") instead of an entirely new number.

When a coin's composition (the metal that it is made of) changes, however, it usually does not get a whole new KM number (as long as the design stays the same). Instead, a letter is added to the KM number to signify the change in materials. For example, Singapore's KM#1 is the 1 cent coin made of bronze; the copper-clad steel version is KM#1a.

It is imporant to note that KM numbers are only unique within a country - most countries have their own "KM# 1". They also usually aren't specific to a year - Switzerland's KM# 29 (20 rappen) starts in 1881 and continues to this day. In order to properly refer to a coin you should include:

• KM number 
• Country
• Year
• Denomination

For example: Netherlands 1 Gulden 1973 KM# 184

As you can see from this example, in many cases the KM number is actually unnecessary to identify a specific coin. The country, denomination, and year are sufficient to pinpoint the coin being discussed. The most crucial use of KM numbers occurs when there are multiple designs for a single year. For example, the India 10 paise coins between 1988 and 1993 were issued in 2 different styles - a scalloped coin (KM# 39) and a plain round coin (KM#40). In this case, using the KM number would help communicate which coin you are referring to.

Because of the way the numbers have to be assigned, KM numbers are not very useful for organizing coins in a collection. Numbers that are close to each other could represent different designs of the same coin, or completely different coins. If you stored your collection in KM# order, it would probably look a little funny. And it is very difficult to find a coin in one of the Standard Catalog of World Coin books by KM number and country alone, because the catalog is organized by denomination and year. However, it is common to write KM numbers on the coins in your collection (usually on the back of your protective coin flips) so that, should you need to know them, you don't have to repeatedly look up the coins in a catalog.

Other Catalog Numbers

The Standard Catalog of World Coins was not the first to assign numbers to coins. Even within the Catalog there are references to coin numbering systems that were introduced by other catalogs and are in common use. While KM numbers are probably the most familiar for world coin collectors, you may also run across:

• Y#: Modern World Coins and Current Coins of the World - Richard S. Yeoman
• C#: Coins of the World, 1750-1850 - William D. Craig
• K#: Illustrated Catalog of Chinese Coins - Eduard Kann

Reading Thai Numbers and Dates

Thailand 1962 1 baht

Thailand, located in southeast Asia a little south of China, is another country that does not use Western Arabic (European) numerals (0, 1, 2, 3...) to represent numbers. In order for coin collectors in the United States, Europe, and similar locations to properly identify both the denomination and year of a Thai coin, it is useful to know how to translate Thai numbers and dates to their European equivalents.

The Thai Numerals

The symbols that the Thai language uses to represent the numbers 0 through 9 are known as Thai numerals and are based on older symbols known as Khmer numerals. Below is a chart showing the Thai numerals that represent the Western Arabic numerals 0 through 9:

The Thai numeral system is a positional number system, so numbers larger than 9 are constructed as they would be using Western Arabic numbers:

• 10 = ๑๐
• 23 = ๒๓
• 496 = ๔๙๖

On coins, the denomination (value) of a coin is usually followed by the Thai word บาท ("baht", the name of the Thai currency).

Here are some examples from actual Thai coins:

Left to right: 1, 25, and 10

To translate Thai numbers, you just replace the Thai symbols with their Western Arabic equivalents (there is no calculation involved, unlike Japanese numbers). Some more recent Thai coins include the denomination in Arabic numerals (note the "10" on the right-most coin).

Thai Dates

Once you can translate the Thai numbers, converting the date on Thai coins to the Common Era (e.g. 2013) is done by subtracting 543 from the Thai year. (Wikipedia has more information about the Thai Solar Calendar for those that are interested.)  The coin's year usually follows the initials พ.ศ. ("B.E.", which stands for Buddhist Era).

Here are date examples from actual Thai coins:

Left to right: 2551 (2008), 2543 (2000), and 2552 (2009)

Collectible Coins Versus Circulating Coins

If you browse the coins available for sale at a large world mint like the Royal Canadian Mint, alongside uncirculated and proof sets of the country's regular coins you'll probably see some fancy coins. Very fancy coins. Coins with color pictures on them, or crystals embedded in them, or coins made of silver and gold (or both at the same time), or coins in special shapes. And you may ask yourself, "Do people in that country walk around with such spectacular coins in their pockets all the time? That would be awesome!"

It would be awesome to have such a variety of coins in use, but these coins are not meant to ever be spent. Mints have the technology and expertise to make coin-like objects, so many branch out and use this power to create collectible coins (also known as collector coins) - special, limited-run coins that usually both commemorate some important person, place, thing, or event, and which frequently make use of technology, design, or materials that would be too expensive in an every-day coin. In recent years, it's not uncommon to also find tie-ins to movies (The Hobbit, Transformers) or well-known characters (Scooby-Doo, Dr. Who).

Canada's 2012 Prehistoric Animals dinosaur
collectible coin with glow-in-the-dark skeleton

One such coin is pictured here. This is the Royal Canadian Mint's first coin in their "prehistoric animals" series, issued in 2012. It has 2 special features that you wouldn't find on pocket change. First, the full-color picture of a Pachyrhinosaurus Lakustai on the back, which is common for collectible coins (it helps them really stand out compared to regular coins). Second, a glow-in-the-dark skeleton of the animal will appear if you shine a light on the picture and then take it into the dark. (This glowing feature is one of the major selling points of this series, and it generated quite an Internet buzz when it was first announced.)

Collectible coins have a denomination (value) on them so that they can be considered a coin instead of a medal or token. This technically makes them legal tender (able to be spent), but the cost of acquiring the coin makes it impractical to actually spend. For example, the Pachyrhinosaurus coin pictured above has a denomination of 25 cents (Canadian), but it will cost $30 to get one - 120 times the value printed on the coin itself.

In contrast, circulating coins are the coins that you use on a daily basis - you get them as change, you find them on the ground, or you spend them in vending machines. These coins are made of inexpensive metal, the design doesn't change very often, and the mints produce thousands if not millions of them each year. You usually don't buy these coins directly from the mint - banks trade in old, worn-out coins for new coins from the mint so that the number of coins in use stays around the same. To get a circulating coin, you either get it as change from a sales transaction, or you can go directly to a bank and "buy" one by trading in an equal amount of money (for example, trading 1 dollar for 4 25-cent coins). (One exception to this are mints, like the US Mint, that sell bags or rolls of uncirculated coins.)

Because of their higher cost, you need to protect collectible coins differently than you would protect regular circulating coins. A folded paper flip isn't going to be enough. Many collectible coins sold today come in their own protective hard-plastic container. This protects them from dust, scratches, water, fingerprints, and other wear (and should never be opened). If you get a collectible coin that doesn't have such a container, visit your local coin shop and get something that will fit the coin securely and tightly - you don't want it to slide around in its protective case.

As a world coin collector, you can specialize in either collectible coins, circulating coins, or of course both. Because collectible coins are so much more expensive, it is more common to start out collecting circulating coins (especially for kids). However, collectible coins make great gifts, especially if you find one with a subject that the recipient will find interesting.

Small World Coins

In the United States, our smallest circulating coin is the dime (10 cents). Its diameter is 18mm (a little less than 3/4 of an inch), which is only 1mm smaller than the penny (1 cent). The size difference is not easily noticed, which is why the dime is a different color (silver) and has a reeded edge to make the 2 coins more distinguishable.

While the dime seems pretty small, there have been plenty of modern world coins which are even smaller. The main reason to mint a small coin is, of course, to use less metal (which makes the coins less expensive to make). But from a practical sense, a country probably can't make all of its coins small because it would be more difficult to tell them apart. And smaller coins are easier to lose, which is why typically only the lowest denomination (value) coins which are made small.

There is also a practical limit to how small a coin can be. It has to be big enough to be able to read the information on it (year, country, value) and heavy enough to not blow away in a light breeze.

The prize for smallest circulating coin issued since 1900 probably goes to Panama's 2 1/2 centismo, which was issued in 1904 and then again from 1975-1982. This coin was only 10mm wide (almost half the size of a US penny), and due to its tiny size received the nickname "Panama Pill". A 10mm coin seems like it would be difficult to use and easy to lose. In 1907 a new 2 1/2 centismo was minted which measured in at a whopping 21mm (in comparison).

Here is a list of many of the small coins which have been issued around the world since 1900. If you know of anything missing from the list, let us know in a comment.

Algeria 1 centime
Argentina 1 centavo
Armemia 10 luma
Aruba 5 cents
Australia 1 cent, 3 pence
Azerbaijan 1 qepik
Bahamas 1 cent
Bahrain 25 fils
Bangladesh 1 poisha
Belgium 25 centimes
Bolivia 2 centavos
Brazil 5 centavos, 20 reis
Brunei 5 sen
Bulgaria 1 stotinki
Cambodia 50 riels
Costa Rica 5 centimos
Ceylon 1 cent
Chile 5 centavos, 1 peso
China 1 fen
Croatia 1 lipa
Cyprus 1 cent
Czech Republic 10 haleru
Finland 1, 10 penni
Denmark 1, 5 ore
Egypt 1/10 qirsh
Euro 1 cent
Guatemala 1/4 real
Iceland 10 aurar
India 10 paise
Japan 1 sen
Kazakhstan 1 tenge
Mexico 5, 10 centavos
The Netherlands 1/2, 10 cents
Netherlands Antilles 1 cent
Norway 10 ore
Pakistan 1 pie
Panama 2 1/2 centismo
Philippines 1 sentimo
Poland 1 grosz
Romania 5 bani
Russia 1 kopek
Singapore 1 cent
South Africa 1 cent
Spain 1 peseta
Thailand 25 satang
Turkey 1 kurus
United Arab Emirates 1 fil