The T89 cartridge converter was a 60 to 72 pin adaptor that allowed people to plug a 60-pin Famicon game into a 72-pin-based NES.

History

The original Nintendo console released in Japan (The Famicon) used a 60-pin cartridge for games. When Nintendo decided to market it outside Japan they redesigned a number of things, including changing the cartridge system to a 72-pin setup. This is, of course, problematic for anyone wishing to play Japanese games on a NES, and thus a number of companies (including Nintendo themselves) produced an adaptor to allow 60-pin games to be played in 72-pin systems.

Interesting Facts

Due to a production overrun of the two R.O.B. games (Gyromite and Stack-Up ) in Japan, Nintendo ended up selling these two games in the US with an internal adaptor. The game itself looks perfectly normal, but inside are the electronics from the Japanese version plugged into a 60 to 72 adaptor. This has contributed to a shortage of the two games, with people looking for a cheap adaptor disassembling these games.

European versions, however, are the standard electronics found in later games.