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The first two letters of the code are the two letters of ISO 3166-1 alpha-2 country codes ( which are also used as the basis for national top-level domains on the Internet ) and the third is usually the initial of the currency itself.

So Japan's currency code is JPY — JP for Japan and Y for yen.

This eliminates the problem caused by the names dollar, franc and pound being used in dozens of different countries, each having significantly differing values.

Also, if a currency is revalued, the currency code's last letter is changed to distinguish it from the old currency.

In some cases, the third letter is the initial for " new " in that country's language, to distinguish it from an older currency that was revalued ; the code sometimes outlasts the usage of the term " new " itself ( for example, the code for the Mexican peso is MXN ).

Other changes can be seen, however ; the Russian ruble, for example, changed from RUR to RUB, where the B comes from the third letter in the word " ruble ".