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 23 Belgium, Bosnia and Herzegovina, Bulgaria, Cuba, Czech Republic, Finland, France, Ghana, Hungary, Iceland, India, Indonesia, Islamic Republic of Iran, Italy, Kazakhstan, Poland, Romania, Serbia, and Thailand. ISO/IEC JTC 1/SC 23 currently has 145 published standards within the field of digitally recorded media for information interchange and storage, including: ISO/IEC JTC 1/SC 23 ISO/IEC JTC 1/SC 23 Digitally recorded media for information interchange and storage 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), which develops and facilitates standards within the field of removable digital