Have you ever gone hunting for treasure? This couple didn't even have to try! They had been walking over it, around it and past it for years. A couple in California couple were walking their dog when they stumbled across what is believed to be one of the largest discoveries of treasure in U.S. history: $10 million in rare, mint-condition gold coins buried in the shadow of an old tree. The coins have been identified as "gold rush era" (1847 to 1894) coins when the news of gold brought some 300,000 people to California from the rest of the United States and abroad. “I don’t like to say once-in-a-lifetime for anything, but you don’t get an opportunity to handle this kind of material, a treasure like this, ever,” said veteran numismatist Don Kagin, who is representing the finders. “It’s like they found the pot of gold at the end of the rainbow.” The gold pieces are only worth about $27,000 (€19,647) based on face value, but some of them are so rare that they could fetch nearly $1 million apiece. They are loaning some to the National Money Show, which opens Thursday in Atlanta before they sell them. Experts say the coins weren't swooped up all at once in a robbery, but were used a personal bank by whomever put them in the ground. The coins, in $5, $10 and $20 denominations, were stored more or less in chronological order, said David McCarthy, chief numismatist with the 1840s and 1850s pieces going into one canister until it was filed, then new coins going into the next one and the next one after that. “I don’t like to say once-in-a-lifetime for anything, but you don’t get an opportunity to handle this kind of material, a treasure like this, ever,” said Kagin. “It’s like they found the pot of gold at the end of the rainbow.”