So I was reading a lengthy article at Gamespy about game rating systems throughout the world, when I came across this box shot of Probotector. (I always thought it was Protobector, but never mind.)
http://www.gamespy.com/articles/652/652162p4.html
Look at the text in the lower-right corner:
What exactly does this mean? I assume the "NES version" would be the North American NTSC NES, but what's this Mattel version?This Game Pak may not be used with the Mattel or NES versions of the Nintendo Entertainment System