CONGRATULATIONS: You now have one of the most remarkable microprocessor game systems available, the MODULAR GAME SYSTEM.
The MODULAR GAME SYSTEM (MGS) offers unmatched flexibility and freedom from the problems of becoming updated and obsolete. This flexibility and freedom is accomplished by the use of interchangeable game modules in combination with the basic game system; however it is necessary to have both, the basic game system and one of the game modules before playing a game. With the MODULAR GAME SYSTEM it is possible to play any one of the several games with the same basic game system by changing the game modules, or to update your MODULAR GAME SYSTEM by use of the latest version of the game module as they become available.
Excerpt taken from the Modular Game System User Manual 1979
The MODULAR GAME SYSTEM has a plastic chess board surface, whereas the GREAT GAME MACHINE has a leather chess board surface.