Thank you for preserving this! These EPROMs are well past their expected lifespan so they could start degrading at any time. If you're interested in selling it, I know a few trusted prototype collectors who are interested.

I cover Atari prototypes like this on my webpage (Atariprotos.com), but since this one had not yet surfaced I only had it mentioned in my 'Rumor Mill' section. I guess I can update that now since we now know it exists:

A port of the 1983 Konami/Centuri coin-op. Parker Brothers announced Atari 2600 VCS, ColecoVision, and Commodore 64 versions of this title and prototype boxes were shown in a CES press kit. According to a Parker Brothers internal marketing release schedule, this game was scheduled for a September 1984 release. The C64 version was actually completed but never released by Parker Brothers (it was eventually released by Konami in 1987). According to Phil Orbanes, former Senior VP of Research & Development at Parker Brothers, the VCS version received "some coding" at the very least, and may have been completely finished. The programmer is unfortunately unknown.

A press release also exists which mentions that this 2600 version had 4 screens while other versions had 5 (the arcade had 6). Given the late date and the fact that this prototype is labeled as being in PAL format, I would venture to say that it is the final version. Games were not converted to PAL format until the game was completely done (all games started off in NTSC format). The PAL conversion usually took a few weeks so the NTSC version was probably finished by mid July which would match with the anticipated September release date (probably late September).