In what a currency expert tells the San Francisco Chronicle is the equivalent of "finding an original Picasso at a garage sale," a rare coin from the California gold rush has been unearthed—said to be one of only four still in existence. The Independent reports the unnamed owner of the $5 Liberty Head Half Eagle—of which 268 total were made by the San Francisco Mint in 1854, per CoinWeek—didn't think the coin was real, and coin experts had told him as much. But one dealer thought it would be worthwhile to get one more opinion, and so the owner handed the coin over to third-party authenticator Numismatic Guaranty Corporation, which set about on a complex course of detective work to compare the new coin to the three existing ones.
Gizmodo explains that wasn't an easy task: Although it had high-res scans of two of the coins (one at the Smithsonian, the other owned by a coin-collecting family called the Pogues), the third coin had been owned by the Du Pont family—and had been stolen in 1967 and never found. Authenticators used images of the Du Pont coin from 1962, when it had last been auctioned off, to establish both that it wasn't the stolen coin and that commonalities among all four coins proved this newest coin was the real deal. NGC won't put an exact number on the coin's value, as it specializes only in authentication, but estimates it's worth "millions." Meanwhile, the only clue to the owner: It's a guy who has lived in New England his whole life, and he's now going to be "quite rich," a coin expert tells the Chronicle. (A single coin dropped in a Salvation Army kettle turned out to be worth a lot.)