ISO/IEC 7812
ISO/IEC 7812 Identification cards – Identification of issuers is an international standard published jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). It specifies "a numbering system for the identification of the card issuers, the format of the issuer identification number (IIN) and the primary account number (PAN)", and procedures for registering IINs.