Aug. 11 (UPI) -- A box of games brought into a Wisconsin retro store turned out to contain a video gaming history mystery: 97 copies of a previously unknown variant of Super Mario Bros./Duck Hunt for the original Nintendo. The seller told Braun the box had wound up in the possession of his grandfather, who worked for a precious metal recovery service. A closer examination soon revealed the games were highly unusual -- a variant edition of the cartridges that were previously completely unknown to the gaming community. "We were shocked," Claire Shelton, head of PSA Video Games, told IGN. As for the rest of the cartridges, 60 were rated 9.8, 31 were rated 9.6 and one was rated 9.4.