The Swiss franc (plural: francs; in German: Frank, plural: Franken) has been the currency of Liechtenstein since 1920. The Swiss franc is legal tender since Liechtenstein is in a customs and monetary union with Switzerland. The 1980 treaty between Switzerland and Liechtenstein allows Liechtenstein to mint limited amounts of Swiss francs with a Liechtenstein inscription, but only in the form of commemorative coins (mainly issued for collectors), and they are not allowed to issue banknotes.
Liechtenstein used the Austrian krone and heller until 1920, and switched to the Swiss franc due to the krone's instability. Liechtenstein coins are so rare that they do not actually circulate, and no banknotes have been issued, with the exception of three emergency issues of heller in 1920. Most of the Liechtenstein franc coins have the same amount of precious metal as the Swiss franc, except for the coins minted in the late 1980s and 1990s.