LOS ANGELES (AFP) - A California couple who unearthed a treasure trove on their property are a few million dollars richer after buyers seized on the ancient gold coins sold at auction.

The unnamed couple uncovered eight cans filled with more than 1,400 coins in March, in what is believed to be the most valuable treasure trove ever discovered in the United States.

On Tuesday night they went on sale, and made more than US$1 million (S$1.26 million) within the first hour, said Don Kagin of Kagin's Inc, a firm specialising in ancient coins, which valued the whole horde at US$10 million.

Just on Tuesday sales on online retail giant Amazon's website and Kagin's own site notched nearly US$4 million, Kagin told AFP.

Proceeds from the first coin to be sold, a US$20 piece dating from 1874 which was snapped up for US$15,000, went to help the San Francisco Mint's restoration fund, he said.

Nearly half the horde was sold within the first 24 hours, he added.

The so-called Saddle Ridge Treasure trove is named after a feature on the couple's property in an area of northern California known for buried treasure since the Gold Rush in the 19th century.

The couple, named only as John and Mary, said they were simply taking their dog for its daily walk when they made the find.

"I never would have thought we would have found something like this. However, in a weird way I feel like I have been preparing my whole life for it," said Mary at the time.