Here's one that can be moved from the rumor mill to the prototype section.
I just picked up a 7800 High Score cartridge prototype from a former Atari engineer.
http://www.digitpress.com/DP/cmf/game.cmf?gameid=2003

Here's some links to pictures so you can verify.
http://www.atari7800.org/labelscans/Hiscore1.jpg
http://www.atari7800.org/labelscans/Hiscore2.jpg

Mitch