The origin of this history is the codes produced by the International Standards Organization (ISO) for currencies and for countries. The ISO has established two- and three-letter codes for almost every country in the world, as well as some geographic territories (such as islands). These codes are easily recognized whenever you receive e-mail. The two-letter code at the end of the Internet address is the ISO two-letter code for that country (CA for Canada, JP for Japan, etc.).
The UN Statistics Division code has to change whenever the territory of a country changes because the code is used to identify data relating to all sorts of statistics e.g. population of a country or trade with foreign countries. The alphabetic codes change whenever the name of a country changes significantly because ISO 3166-1 does - properly speaking - not code countries but names of countries.
The ISO has also established three-letter codes for most of the world's currencies. The codes change whenever a country replaces an existing currency with a new currency. For example, when Mexico introduced a New Peso in 1993, the symbol for the Mexican Peso was changed from MXP to MXN. When the Soviet Union split apart, creating 15 new countries, each new country was assigned a currency code when it introduced its own currency.
The ISO does not provide codes for all currencies. The reason for this is that the money-issuing authority within that country must apply to the ISO for a new currency or country code. Curencies may not have currency codes for several reasons. First, some countries, such as Somaliland or Transdiniestra that are not internationally recognized, do not have country or currency codes. Second, countries may not apply for new codes when they introduce a new currency. Yugoslavia was under international sanctions in 1993, and did not apply for new codes while it went through four currencies in 1993 and 1994. Third, the ISO has not set up any historical currency codes for currencies that no longer exist.
The goal of this history is to provide a single set of currency codes for all existing and historical currencies to the beginning of the Twentieth Century, as well as codes for some currencies that existed before 1900. Whenever the ISO has provided a code for a particular country, we use their code. If the ISO has not provided a code, we have created a three- or four-letter code for that currency.