This seems to be the most commonly found NES Test Cartridge as it was used in conjunction with the NES Test Station. They seem to be slightly more abundant than their yellow colour cousins.
NES test make the system hardware and accessories run through tests to make sure that internal and external equipment all work properly. Testing Video RAM, colors, control ports, Power Pads, joysticks, etc.
Two completely different versions of this cart exist, although the labels remains identical.
This seller has seven Game Boy Protoypes. All are a bit more than they would fetch at open auction. He has some nice rarities as well.
Complete Nintendo Virtual Boy Console with All 14 US Releases & Hard Case Bundle
Set Of 2 Vintage Nintendo Wallets-NOS-1988-Blister Pack-Item
New Super Mario Bros. Bundle, New Sealed! Nintendo DS VGA 95 – Really? Come on.
Dragon Feet NES home brew game from TooManyGames gaming expo – Apparently I should have bought one of these when it was offered to me.