ISO 4217 "ruble". In addition to codes for most active national currencies ISO 4217 provides codes for "supranational" currencies, procedural purposes, and several things which are "similar to" currencies: The use of an initial letter "X" for these purposes is facilitated by the ISO 3166 rule that no official country code beginning with X will ever be assigned. Because of this rule ISO 4217 can use X codes without risk of clashing with a future country code. ISO 3166 country codes beginning with "X" are used for private custom use (reserved), never for official codes. For instance, the ISO 3166-based NATO country
International Organization for Standardization a committee. Here are some abbreviations used for marking a standard with its status: Abbreviations used for amendments: Other abbreviations: International Standards are developed by ISO technical committees (TC) and subcommittees (SC) by a process with six steps: The TC/SC may set up working groups (WG) of experts for the preparation of a working drafts. Subcommittees may have several working groups, which can have several Sub Groups (SG). It is possible to omit certain stages, if there is a document with a certain degree of maturity at the start of a standardization project, for example a standard developed by another