A few years ago, a pop culture store owner in Wisconsin mentioned to Jason Ganos, a well-known Nintendo game collector, that he had a box of Super Mario cartridges that had been sitting in storage for years. It stopped Ganos in his tracks.

It turned out to be an ultrarare collection of 97 "absolutely pristine” copies of Super Mario Brothers Duck Hunt, a popular Nintendo game that was released in 1988, Ganos said.

After some initial research, Ganos found that the cartridges he held were not only a new variant of the game, but also the last known production date of it.

Most of the cartridges will go up for sale Friday in an online auction that will run until Sept. 9.

"I still don’t quite believe that any of this is happening,” Ganos said. "I just think it’s kind of serendipitous that this happened. It’s just still very bizarre to me.”