For future treasure hunters, the man who discovered a rare and valuable photograph of Billy the Kid playing croquet has some advice: go rummaging.

Randy Guijarro told the Guardian on Monday, “I hope this motivates others out there to dig into trunks and attics because there are so many lost treasures out there.”

In 1878, a detail from a 45-inch photograph shows Billy the Kid, left, playing croquet.

A $2 junk store find turned into a multimillion-dollar photograph of Billy the Kid playing croquet.

Guijarro spent $2 for the four-by-five-inch tintype and two other images he found in a cardboard box in a Fresno, California, antique shop in 2010. Its current value is estimated to be in the millions of dollars.

The telecommunications technician and his wife, Linda, said they plan to use some of the money from their unexpected find to fund additional expeditions.

“We may benefit from a new automobile.”

We’d like to search for forgotten parts of history in the United States and around the world.

We enjoy going on adventures. The hunt is a truly magnificent event.”

He recognized Henry McCarty, better known as Billy the Kid in Wild West lore, as the man leaning on a croquet mallet, along with members of his gang, the Regulators, playing the sport in New Mexico in 1878, after studying the image under a microscope at home.

The discovery, which is only the second confirmed photograph of the criminal, is estimated to be worth $5 million.

In a broadcast on Sunday, a National Geographic program narrated by Kevin Costner chronicled the five-year attempt to authenticate it — a forensic and historical odyssey.

“It was fantastic.” “It was really difficult for us to witness it,” said Guijarro, 54. “We’ve laid it all out for you, told you the truth, and we hope you’ve had a good time along the way.”

He added that skepticism and false leads plagued the investigative work, leaving the pair uncomfortable and anxious, unsure who to believe.

“It has its highs and lows.” It had been a long and lonely voyage. This image had a Twilight Zone vibe about it. “It’s far too good to be true.”

Billy the Kid, a New Yorker who forged a brief, murderous career as an outlaw, allegedly killing 21 men before being gunned down by Lincoln County sheriff Pat Garrett in 1881, at the age of 21, is synonymous with the Wild West.

According to other historians, he only killed nine individuals. The only other photo of him that has been confirmed is a shot of him sitting with a rifle taken in 1880 that sold for $2.3 million (£1.5 million) in 2011.

Guijarro has collected coins, sports cards, comic books, and other memorabilia for most of his life, frequently collaborating with his wife, who enjoys antique photographs.

He was traveling home alone from work in late summer 2010 when he came across Fulton’s Folly Antique Collective in Fresno’s Tower neighborhood.

The dealer sent him to two men carrying “junk crates.” Guijarro was informed that they were cleaning out a storage space and wanted to dispose of it.

He chose three images — the croquet players, as well as other 19th-century scenes – and offered $2, which was all he had. It was taken by them.

Guijarro has little recollection of them. “I didn’t know who they were.” It’s almost like a blur.”

He admired the croquet shot’s composition, but it took him a week to inspect it under a microscope and recognize the legendary bandit.

“You could hand him a Winchester rifle.” It was his hat, his attitude, and the fact that he was leaning on a croquet stick. “My goodness, it’s Billy the Kid,” I reasoned.

Linda was summoned – he describes her as “a lovely, sensible woman” – and she conducted research on other members of the Regulators.

She discovered Tom O’Folliard and Charlie Bowdre, two more croquet players, over the internet. “It was just stunning,” Guijarro added.

They eventually recognized all 18 persons in the photo, as well as the schoolhouse in Chavez County, New Mexico, whose remains they discovered, with the help of researchers, collectors, facial recognition experts, and other specialists.

It discovered out that the shot was taken after a wedding in 1878, only a month after the gang took part in the bloody Lincoln County conflict.

Kagin’s Inc, a numismatic firm based in California, has insured it for $5 million and is looking for a private buyer.

“We’re not counting our chickens before they hatch,” Guijarro added, “but there’s a lot of curiosity out there.”

He and Linda intend to pay off bills, assist some friends and relatives, and begin plotting future treasure hunts in addition to purchasing a new car.

They aren’t hoarders, he claims, because they sell practically everything they come across. “We’d be sitting on a hundred acres of stuff else.” It’s all about going on a hunt.”