Nintendo Wideboy 64 CGB (with Gameboy Color attachment)
Developers tool to play and debug and demonstrate Gameboy Color and Gameboy cartridges 
through a Nintendo 64 system using either a GameBoy attachment or Nin64 controller.

This is a developers cartridge the Wideboy 64 CGB and attachment made by the only authorized developmental tool creators for Nintendo items, Intelligent Systems. 
The cartridge would plug directly into a Nintendo64 game system to allow for Gameboy and Gameboy COLOR cartridges to be displayed through a full monitor and which could be controlled by either using the Nintendo64 controllers or the Gameboy attachment as a controller (as shown in the picture). This would allow for more people, developers, producers, and decision makers to see and experience the  game play and action in a larger presentation. These units would also allow for individual sprite manipulation as well as better screen shots to be taken. These are also used for game shows in which the companies would want their games to be displayed on larger monitors so more people could see the game in action. The attachment is really a nice addition.
These units could only be bought from Nintendo directly at a cost of $1700.00 each.