9 most valuable U.S. coins
5. Three dollar gold piece (S)
90% gold, 10% copper
You can thank the U.S. postal system for this incredibly valuable coin. At the time of the minting of the three-dollar gold piece, a stamp cost three cents and was typically sold in sheets of 100. Thus, a three-dollar coin came in mighty handy when buying a roll of stamps. Only one 1870-S was thought to have been struck, specifically to be sealed within the cornerstone of the then-new San Francisco Mint. But in 1982, a second 1870-S turned up in the market and was purchased by legendary collector Harry Bass for $687,500.
Shortly after the coin was installed in the Mint, it was removed from the cornerstone. To date, this 1870-S has never been recovered. Don't bother charging up your metal detector – the coin was probably badly damaged when it was extracted from the stone. The existing 1870-S was once used as a watch fob by the former Chief Coiner of the San Francisco Mint. Nice work if you can get it.