SMS Power founder Bock has posted images of a recently unearthed prototype copy of NBA Jam for the Sega Master System. It's a notable find, as the game was never officially released anywhere in the world.

While NBA Jam saw a Game Gear port in 1993, the Sega Master System version is dated for 1994, and includes a fully functional head-to-head multiplayer mode -- something that was absent from the Game Gear edition and its sequel, NBA Jam Tournament Edition. Bock speculates that the port was created in-house by now-defunct Acclaim developer Iguana Entertainment.

The game will be released to the public shortly, and further dissection should hopefully reveal more about its origins.