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
ISO/IEC JTC 1/SC 2 to the ISO/IEC 10646 standard (covered by ISO/IEC JTC 1/SC 2/WG 2) and amendments to the ISO/IEC 14651 standard (covered by ISO/IEC JTC 1/SC 2). ISO/IEC JTC 1/SC 2 ISO/IEC JTC 1/SC 2 Coded character sets is a standardization subcommittee of the Joint Technical Committee ISO/IEC JTC 1 of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), that develops and facilitates standards within the field of coded character sets. The international secretariat of ISO/IEC JTC 1/SC 2 is the Japanese Industrial Standards Committee (JISC), located in Japan. ISO/IEC JTC 1/SC 2 was established in 1987, originally