SAN FRANCISCO (AP) — A treasure trove of rare gold coins discovered by a California couple out walking their dog has gone on sale, with one coin selling for $15,000 on Tuesday. 
 
 FILE - This Feb. 25, 2014 file photo shows some of the 1,427 Gold-Rush era U.S. gold coins displayed at Professional Coin Grading Service in Santa Ana, Calif. A treasure trove of rare gold coins discovered... (Associated Press) 
 
 The coins date from 1847 to 1894 and have been valued at $11 million. 
 
 Several coins were auctioned at the Old San Francisco Mint at 8:30 p.m. Tuesday, and one of them — an 1874 $20 double eagle that is usually worth $4,250 — sold for $15,000. 
 
 Don Kagin, whose firm is handling the sale, says most of the remaining 1,400 coins had gone on sale on Amazon.com and Kagins.com after the auction. 
 
 The couple, whom Kagin declined to identify, found them last year buried under the shadow of a tree on their rural Northern California property. 
 
 Here are five things to know about the coins and their origin: 
 
 WHY ARE THEY SO VALUABLE? 
 
 Experts say paper money was illegal in California until the 1870s, so it's extremely rare to find any coins from before that period. Additionally, most of the coins are in mint condition, having been stashed away seemingly immediately after they were minted. They were valued by Don Kagin, a numismatist who is handling the sale and marketing of the coins. 
 
 WHO FOUND THEM? 
 
 Kagin says the couple — a middle-aged husband and wife — does not want to be identified in part to avoid a gold rush on their rural Northern California 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 themselves and use the money from the rest to pay off bills and donate to local charities. Money from Tuesday's auction will benefit the effort to turn the Old Mint into a museum. 
 
 WHERE DID THE COINS COME FROM? 
 
 Most of the coins were minted at the San Francisco Mint, according to Kagin. It's not clear, however, who put them in the ground or how they were obtained, though theories have abounded. 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. 
 
 WHAT IS IN THE COLLECTION? 
 
 The treasure consists of four $5 gold pieces, fifty $10 gold pieces, and 1,373 $20 double eagles. Among the coins that will be on display Tuesday is the crown jewel of the collection — an 1866-S No Motto $20 gold piece valued at more than $1 million. 
 
 HOW DOES THIS DISCOVERY COMPARE TO OTHER COIN FINDS? 
 
 Kagin calls this coin find the largest such discovery in U.S. history. One of the largest previous finds of gold coins was uncovered by construction workers in Jackson, Tennessee, in 1985 and valued at $1 million. More than 400,000 silver dollars were found in the home of a Reno, Nevada, man who died in 1974 and were later sold intact for $7.3 million. Gold coins and ingots said to be worth as much as $130 million 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. ||||| A California couple who found a stash of buried gold coins valued at $10 million may not be so lucky after all. The coins may have been stolen from the U.S. Mint in 1900 and thus be the property of the government, according to a published report. 
 
 The San Francisco Chronicle's website reported that a search of the Haithi Trust Digital Library provided by Northern California fishing guide Jack Trout, who is also a historian and collector of rare coins, turned up the news of the theft. 
 
 WATCH: $10M Gold Coins May Be Linked to Heist 
 
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 The California couple, who have not been identified, spotted the edge of an old can on a path they had hiked many times before several months ago. Poking at the can was the first step in uncovering a buried treasure of rare coins estimated to be worth $10 million. 
 
 "It was like finding a hot potato," the couple told coin expert Don Kagin from Kagin's, Inc. The couple hired the president of Kagin's, Inc. and Holabird-Kagin Americana, a western Americana dealer and auctioneer, to represent them. 
 
 The coins are mostly uncirculated and in mint condition, and they add up in face value to $27,000. "Those two facts are a match of the gold heist in 1900 from the San Francisco Mint," the newspaper reported. 
 
 Jack Trout told the paper that an 1866 Liberty $20 gold piece without the words "In God We Trust" was part of the buried stash, and the coin may fetch over $1 million at auction because it's so rare. 
 
 "This was someone's private coin, created by the mint manager or someone with access to the inner workings of the Old Granite Lady (San Francisco Mint)," Trout told the newspaper. "It was likely created in revenge for the assassination of Lincoln the previous year (April 14, 1865). I don't believe that coin ever left The Mint until the robbery. For it to show up as part of the treasure find links it directly to that inside job at the turn of the century at the San Francisco Mint." 
 
 Mint spokesman Adam Stump issued this statement when contacted today by ABC News: "We do not have any information linking the Saddle Ridge Hoard coins to any thefts at any United States Mint facility. Surviving agency records from the San Francisco Mint have been retired to the National Archives and Records Administration (NARA), under Record Group 104. Access to the records is under NARA's jurisdiction: http://www.archives.gov/." 
 
 Last week, when news of the stash first broke, coin dealer Kagin spoke about the rarity of such a find. 
 
 "Since 1981, people have been coming to us with one or two coins they find worth a few thousand dollars, but this is the first time we get someone with a whole cache of buried coins... It is a million to one chance, even harder than winning the lottery," Kagin told ABCNews.com. 
 
 The couple is trying to remain anonymous after finding the five cans of coins last spring on their Tiburon property in northern California and conducted an interview with Kagin. 
 
 WATCH: $10M Gold-Coin Surprise Uncovered in Calif. 
 
 "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," the couple said. 
 
 "I saw an old can sticking out of the ground on a trail that we had walked almost every day for many, many years. I was looking down in the right spot and saw the side of the can. I bent over to scrape some moss off and noticed that it had both ends on it," they said. 
 
 It was the first of five cans to be unearthed, each packed with gold coins. 
 
 "Nearly all of the 1,427 coins, dating from 1847 to 1894, are in uncirculated, mint condition," said Kagin told ABCNews.com. 
 
 He said that the couple plan to sell most of the coins, but before they do, they are "loaning some to the American Numismatic Association for its National Money Show, which opens Thursday in Atlanta." 
 
 "Some of the rarest coins could fetch as much as $1 million apiece," said Kagin. He also said that they wish to sell 90 percent of the collection through Amazon.com and on the company's website. 
 
 "We'd like to help other people with some of this money. There are people in our community who are hungry and don't have enough to eat. We'll also donate to the arts and other overlooked causes. In a way it has been good to have time between finding the coins and being able to sell them in order to prepare and adjust. It's given us an opportunity to think about how to give back," said the couple. 
 
 Kagin and his colleague David McCarthy, senior numismatist and researcher at Kagin's, met with the couple last April, two months after the hoard was found. 
 
 When McCarthy and Kagin told the couple that their bonanza will be in the annals of numismatic stories for quite some time, the couple said, "It would have been quite a pity not to share the magnitude of our find. We want to keep the story of these coins intact for posterity."
– The "buried treasure" found by a California couple out walking their dog—an estimated $11 million worth of rare gold coins from the 1800s—has started to be auctioned off. Last night at the Old San Francisco Mint, an 1874 $20 double eagle sold for $15,000, the AP reports. A few other coins were also auctioned there, and most of the remaining 1,400 are now on sale on Amazon.com and Kagins.com, according to the firm handling the sale. The anonymous couple, who found the coins on their own property, are also keeping a few. As for the money they make, they'll pay bills and donate to local charities—and the money from last night's auction will help turn the Old San Francisco Mint into a museum. About 60 of the coins will be displayed there, USA Today reports. It's still not clear where the coins, most of which are in mint condition, came from—the numismatist who valued the coins and is handling the sale says theories (none of which panned out) have linked them to stagecoach bandit Black Bart, outlaw Jesse James, and a heist at the San Francisco Mint. And, of course, there are people out there who claim the coins belonged to their distant relatives—one of whom has threatened to sue. But none of the stories so far is legit, according to federal officials.