This prototype was found on a reproduction cartridge put out by
Best Electronics. Best Electronics had access to a lot of
prototype cartridges when they bought some of Atari's inventory in
the mid 80's and they put many of these prototypes on reproduction
cartridges. It is unknown exactly what the date is for the
prototype, but it appears to be based off the final version of the
code, only with the cartridge copy protection enabled and the
easter egg disabled.