Atari were the kings of prototypes, with more documented pieces of prototype hardware available than probably all the other manufacturers put together...
KNOWN *HELP!* - ATARI UNKNOWN 70'S PROTOTYPE GAME LIST
Notes : A straight port of Level 7 from the Atari 2600 console game Air-Sea Battle.
Dirtbike
19?? (Prototype)
No images available
Notes : Designed by Dennis Koble and finished up by Ed Logg. Playtested but not released.
Super Man / Solar War / Orion XIV
1979 (Prototype)
Notes : A kind of sequel to Video Pinball. 5 units were built and around 300 kits sold to a Greek company. Originally to be called Super Man but the licensing deal fell through and they needed another name to fit the 5 3 pattern (because of the drop targets)
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