A California couple found a stash of gold coins buried on their property last year valued at as much as $10m (£6m), rare coin dealers have said.
The 1,427 coins, which date from 1847-1894, were never circulated and are in mint condition, numismatist David Hall told the Associated Press.
The unnamed couple found them buried in rusting metal cans under a tree while on a walk last April.
It is seen as the largest haul of buried treasure in US history.
"We've seen shipwrecks in the past where thousands of gold coins were found in very high grade, but a buried treasure of this sort is unheard of," David McCarthy of currency firm Kagin's, who is advising the couple, told Reuters news agency.
"I've never seen this face value in North America and you never see coins in the condition we have here."
The couple live in a rural area of California known as Gold Country for the swarms of prospectors who descended on the region during the 19th Century gold rush.
They found the coins in an area of their land they called Saddle Ridge, and the coin dealers who have seen the haul have taken to calling it the Saddle Ridge Hoard.
It is a mystery who buried the coins - and why.
Mr Hall of Professional Coin Grading Service of Santa Ana, California, which recently authenticated the coins, told the Associated Press the coins' face value adds up to about $27,000. But some of the coins are so rare they could sell for $1m each.
The couple plan to sell the coins on Amazon.