The 16-year-old Don Lutes Jr. held on to his discovery for over 7 decades until his death this year. Now, the find is expected to fetch over $1 million.

In 1947, 16-year-old Don Lutes Jr. found a rare 1943 Lincoln penny in his lunch money while a high school student in Massachusets. The “most famous” coin is one of the 20 accidentally minted copper coins, whose existence the government even denied for years. Lutes Jr. wisely held on to the penny for some 70 years until his recent death in September.

Now, the coin is going up for auction and expected to fetch anywhere from $1 to $1.7 million.

“This is the most famous error coin in American numismatics and that’s what makes this so exciting: No one really knows what it’s going to sell for,” said Sarah Miller of Heritage Auctions.

Lutes received offers for the coin for years until he approached the U.S. Treasury about it himself. He was assured that “all pennies struck in 1943 were zinc coated steel” and told that what he thought he had was, in fact, a fake. Lutes kept the coin anyway.

A similar penny sold for $1.7 million in 2010, and the current bid with Heritage Auctions hovers at $130,000.