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.”

Ganos, a hard-core fan covered in Nintendo tattoos and who has operated Nintendo Wire, a news service for Nintendo announcements and nostalgia for over 10 years, said he would not venture to guess how much the games are worth.

But when he saw the box, he immediately knew it was special.

“It’s like pulling out like a Holy Grail,” Ganos said, later adding, “They’re gorgeous.”

The discovery came after the owner, Kevin Braun, of One Stop Wonders in Waukesha, outside Milwaukee, asked Ganos to help him sell some stuff, including common Nintendo games and Pokémon cards.

Braun mentioned the box of Mario cartridges that had been sitting in storage for years. He recalled buying them from a customer whose family had kept them for metal scraps but thought they were not worth much.

The cartridges of Super Mario Brothers Duck Hunt he had were made in 1993, long after the company discontinued the bundle in 1991. Braun and Ganos still aren’t sure why the copies they possess were made but assume they were either warranty replacements or part of a bundle with a box retailer that never panned out.

Knowing the potential significance of the possession, Ganos booked a flight immediately.

“I flew down to California with 97 carts in my carry-on luggage, sweating bullets going through TSA, like why do you have 97 little circuit boards in your carry-on?” Ganos recalled thinking nervously.

He anxiously made it through airport security to meet with video game experts to have the cartridges verified and graded, giving them a perceived value.

There had never been a cartridge rated a perfect 10 at Professional Sports Authenticator video games, Ganos said.

Five of the 97 Ganos possessed received a perfect score.

“I think there’s going to be historic significance to the tens,” Ganos said when talking about how much the games may sell at the auction. “Like number one, it’s so many people’s childhoods, and number two, there’s never been a 10 in an NES cart before.”

Ultrarare video game cartridges, especially ones with unique production history, can be sold for six- to seven-figure prices in the collector’s market. Ganos said the 97 carts are also unique because of their perfect condition, which, much like comic books or sports cards, often sell higher.

Ganos can’t estimate the ultimate worth of the cartridges because they are incomparable to other video game collectibles he has seen before. They could be worth hundreds, thousands or tens of thousands, he said.

Ganos and Braun are only auctioning off three of the perfect 10 scored cartridges at Golden Pop’s Culture Auction beginning Friday. They are both keeping one copy with a score of a 10, and a few others rated in the higher 9’s.

The games can be played if the buyer wants. But because they are pristine, Ganos hopes to keep them that way.

“Finding uncirculated stuff for me is just like super exciting,” Ganos said. “This game was the first video game I’ve ever played. Mario Duck Hunt was just such a big part of my life growing up.”

Braun and Ganos also plan to do a charity auction after they are finished with the current one.