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The coins date from 1847 to 1894 and have been valued at 11 million dollars (£6.5 million).
Several coins have already been auctioned at the Old San Francisco Mint, and one of them - an 1874 20-dollar double eagle that is usually worth 4,250 dollars (£2,530) - sold for 15,000 dollars (£9,000), the AP said.
Don Kagin, whose firm is handling the sale, said most of the remaining 1,400 coins went on sale on Amazon.com and Kagins.com after the auction.
The couple found the coins last year buried under the shadow of a tree on their rural northern California property.
Mr Kagin said the couple - a middle-aged husband and wife - do not want to be identified in part to avoid a gold rush on their property by modern-day prospectors.
They discovered the coins in eight cans buried in the shadow of an old tree on the property. They plan to keep a few of the coins and use the money from the rest to pay off bills and donate to local charities.
The treasure consists of four 5-dollar gold pieces, 50 10-dollar gold pieces, and 1,373 20-dollar double eagles. The crown jewel of the collection - an 1866-S No Motto 20-dollar gold piece - is valued at more than a million dollars (£560,000).
Experts say paper money was illegal in California until the 1870s, so it is extremely rare to find any coins from before that period. Most of the coins are in mint condition, having been stashed away seemingly immediately after they were minted.
Most of the coins were made at the San Francisco Mint, according to Mr Kagin. It is not clear who put them in the ground or how they were obtained, although theories have abounded. Mr Kagin says people have linked the coins to stagecoach bandit Black Bart, outlaw Jesse James and a theft at the San Francisco Mint, but none of the theories has panned out.
Mr Kagin calls this coin find the largest such discovery in US history. One of the largest previous finds of gold coins was uncovered by construction workers in Jackson, Tennessee, in 1985 and valued at a million dollars.
More than 400,000 silver dollars were found in the home of a Reno man who died in 1974 and were later sold intact for 7.3 million dollars.
Gold coins and ingots said to be worth as much as 130 million dollars were recovered in the 1980s from the wreck of the SS Central America, but historians knew roughly where that gold was because the ship went down off the coast of North Carolina during a hurricane in 1857.