An unopened cardboard box filled with packs of hockey cards from 1979-1980 sold for a whopping $3.72 million at auction on Sunday, according to Heritage Auctions.

There are 16 boxes of cards in the carton, each filled with 48 packs of O-Pee-Chee hockey cards, according to a news release from the auction house. 

Heritage Auctions said the box might contain two dozen Wayne Gretzky cards from his rookie years. Gretzky, known as one of hockey's all-time greats, played for the Edmonton Oilers at the time the cards were printed.

"We knew from the moment we heard this O-Pee-Chee case existed that it would get the attention of hockey card collectors worldwide," said Chris Ivy, director of sports auctions at Heritage. 

The box of cards was originally owned by a man who was a "rabid collector" in the 1960s and 1970s, according to Heritage Auctions. 

"Remarkably, our consignor wasn't aware he owned this outrageous Holy Grail case until very recent accounting of a long-forgotten pile of boxes in his home in Saskatchewan," Heritage Auctions wrote in the item description. 

The man's son found the case behind "stacks and stacks of other stuff," Heritage Sports card specialist and consignment director Jason Simonds said. 

There were 10,752 "fresh off the factory floor" cards inside the case, which was authenticated before auction, Heritage Sports said.

According to Heritage Auctions, no other unopened case of 1979-80 O-Pee-Chee cards has ever surfaced in the 21st century. 

"By any metric of evaluation, it's a thrilling miracle of survival, and one of the greatest trading card lots that Heritage has ever had the privilege to offer," Heritage Auctions said.

The auction house has not disclosed the identity of the buyer.