Nearly 100 Unreleased Nintendo Cartridges Discovered in Wisconsin Store

A game shop in Waukesha, Wisconsin, found a box containing almost 100 copies of Super Mario Bros. and Duck Hunt cartridges that differ in screws, labels, motherboards and manuals from known versions. The box, marked with a 1993 production year, was purchased two to three years ago by store owner Kevin Braun from a man who had stored the items in his garage for decades. Braun said the cartridges were originally slated for metal recovery but were spared when he learned of their uniqueness.

Jason Ganos, who runs the Nintendo-focused site Nintendo Wire, told ABC News that the cartridges play identically to the classic games but are physically distinct. He suggested they may have been produced as replacement stock for warranty repairs or as part of an unreleased bundle. Ganos added that the find is extremely rare.

Professional Sports Authenticator, a memorabilia grading firm, has graded several of the cartridges a perfect 10, a first for NES games. Three of the items are slated for auction by Goldin Auctions, while a 9.6-graded Super Mario Bros. cartridge recently sold for $3 million at Heritage Auctions, setting a record for the highest-graded sealed edition.

"As an entire collectible market, video games is experiencing an incredible wave," said Claire Shelton, head of PSA Games, in a statement to ABC News.