James Buster Douglas Knockout Boxing is arguably the rarest US Sega Master System release. The argument actually centers on Sonic The Hedgehog which was actually a European copy with an American UPC code sticker over the bar-code. It’s one of those releases that some people count, others don’t. Not the point for this anyways.
The game itself features the short-lived heavyweight boxing champ of the world in 1990, James “Buster” Douglas. Amusingly enough his reign did not last very long after the game was released, loosing in his first title defense to Evander Holyfield. This probably helped to make the game a rarity through limited sales.
The game itself is a variation of the PAL release Heavyweight Champ but with the character swapped to James Buster Douglas and a changed title screen.
For price references, one sold back in January without manual for $125.00.