John Stoner came across the 360-year-old coin in a Nottingham field with a metal detector.
The silver threepenny is from the US and experts believe it was struck in Boston way back in 1652. But they're unsure how it got to this side of the pond.
Treasure hunter John, 42, was on an outing with metal detector club Coil To The Soil, when he stumbled across the extremely rare coin.
But the father-of-two wasn't even aware of its value at first. He was quoted in the Daily Mail explaining: "At first I didn't think it was anything special. I knew it wasn't English, but just how important a find it was, I didn't have a clue."
It wasn't until a snap of the coin was uploaded to the club's Facebook page, that its real worth was discovered, when one member wrote: "Your mate has just won the lottery!"
The coin is set to be auctioned in December and Nottingham-based John will share the money with the field's landowner.
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