"I thought any second an old miner with a mule was going to appear." That was the reaction of a California man who dug up $10 million worth of gold coins he and his wife found while they were walking their dog. It's a story of discovering buried treasure, an idea hard wired in the human psyche. There were 1427 coins — worth $5, $10 and $20 apiece — dated from 1847 to 1894 and minted in San Francisco. The couple that found them has not been identified, but David McCarthy is the numismatist, or coin expert, they consulted after realizing the dream of virtually every human being. He works for the coin dealer Kagin's in Tiburon, California.