The Reporting Body Identifier is the first two digits of a Global System for Mobile Communications (GSM) Type Allocation Code, and indicates the GSMA-approved organization that registered (or, before 2002, approved) a given mobile device, and allocated the model a unique code.
The numbers are loosely based on the telephone country code (CC) of the organization identified, as most approving nations used a single approval body endorsed by their national GSM Association chapter. However, not all Reporting Body Identifiers follow this tendency.
According to Permanent Reference Document TS.06 (IMEI Allocation and Approval Process Version 25.0, 01 May 2024 ), Appendix A of the GSM Association, the current Reporting Body Identifier (RBI) codes indicate the following approval/allocation bodies:
Reporting Bodies that no Longer Allocate IMEIs:
The "Reporting Body Identifier" is also known as the Regional Code in the CDMA context. The International Mobile Station Equipment Identity (IMEI) and Mobile Equipment Identifier (MEID) structures are superficially the same, except that the first two digits must be decimal for an IMEI, and must be hexadecimal for an MEID. In 3GPP2 terms the GSMA is the Global Decimal Administrator while the Telecommunications Industry Association (TIA) is the Global Hexadecimal Administrator.