"I saw an old can sticking out of the ground on a trail that we had walked almost every day for many, many years," said John, who used a stick to dig it out.
They carried it back to the house, despite its considerable weight. "I said to Mary, 'Wow, this thing is heavy. It must be full of lead paint.' I couldn't figure out what in the world would weigh that much," John said.
At that moment, "the lid cracked off and exposed a rib of a single gold coin," he said, adding: "I clamped the lid back on -- I found a can of gold coins and I thought there was a zero percent chance of Mary believing me!
"When I told her, the look of bewilderment -- her mouth was so wide open flies could have flown in and out several times."
Mary added: "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."
After further digging, including with a metal detector, they eventually unearthed eight cans. The couple, who are around 40, have decided to remain anonymous for the moment.