From Retro CDN
When categorising products by country, the Retro wikis use a two-character country code, as defined in the ISO 3166-1 alpha-2 standard.
As these wikis document video games, however, some exceptions are made to conform with trends of video game publishers - "UK" is generally used for the United Kingdom as opposed to the officially designated "GB", and "EU" is used for Europe. Other exceptions are as follows:
On Sonic and Sega Retro, historical reasons mean that "AS", the code for American Somoa, is sometimes used to describe the fictional "Asia" region. For many years, Sega produced "Asian" products for sale across anything in the Asian continent that was not Japan or South Korea. The borders between Europe and Asia under this scheme, however, are vague, with Asian produce being sold in the middle east, parts of Eastern Europe, and even Africa.
BX is used for the Benelux region (Belgium, the Netherlands and Luxembourg). These are typically identified as with dual French and Dutch packaging (and are often referred to as "FR/NL"). Games solely in Dutch are considered to be part of the "NL" region, while those in French can safely be assumed to be made for France.
"EX" is a pseudo country code used by Microsoft and Sony to describe English language European video games not for sale in the United Kingdom.