Sometimes cleaning out your attic can be worth it. For 15 years, Scott Amos' mother had been asking him to come pick up boxes of childhood memorabilia he'd been storing in the attic of her Humboldt County, California home. This past Mother's Day, 40-year-old Amos fulfilled her wish and made an incredible discovery in the process. While he was cleaning out the five boxes, Amos stumbled upon an unopened copy of Kid Icarus, a popular Nintendo video game from 1987. The game, still in a JCPenney shopping bag, had its original pricetag of $38.45, along with the receipt, dating the purchase to December 1988. Amos consulted two video game experts, who agreed that the game would be worth a significant amount to collectors. He put the game up for auction through Heritage Auctions' Comics & Comic Art auction, and last week it sold for a winning bid of $9,000.

Photo courtesy of Heritage Auctions

"To find a sealed copy 'in the wild,' so to speak, not to mention one in such a nice condition and one with such transparent provenance, is both an unusual and rather historic occurrence," said Valarie McLeckie, video game consignment director of Heritage Auctions, in the statement. According to Heritage Auctions, there are fewer than 10 known sealed copies of Kid Icarus. Denver-based Wata Games, a video game collectors' grading service, rated Amos' copy of the game an 8 out of 10. McLeckie says she's seen a lot of games come across her desk, but Amos' find stands out. "It's certainly one of the most surprising just because of the origin of the game and how it was found," McLeckie tells CNBC Make It. "Typically, these higher-end, rare titles that we receive on consignment are from collectors who know what they have, and in the case of Kid Icarus, it was found in someone's attic with the receipts and the price sticker still on it so it also has a clear chain of provenance, which is very unusual as well in this type of collectible."

Photo courtesy of Heritage Auctions