A portion of a 4×5-inch photo showing Billy the Kid, left, playing croquet in New Mexico in 1878. Discovered in 2010, the photograph is only the second verified image of the notorious outlaw. (Courtesy of Kagin’s)

As legend has it, Billy the Kid was a cold-blooded outlaw and cattle rustler who lived hard and died young.

Less legendary, it turns out, is the fact that the kid — a.k.a. William Bonney — was a player of the popular 19th century British pastime known as croquet.

That’s according to only the second photo ever to be confirmed of the infamous outlaw, whose short life and mysterious death continue to fascinate historians and bewitch investigators.

[One man’s quest to bury the Wild West mystery of Billy the Kid’s death]

The photo, discovered by a collector inside a Fresno, Calif., junk shop in 2010, was purchased for $2 at the time. Since it was recently authenticated by Kagin’s — a San Francisco-based company specializing in Western Americana and Rare Coins — the image’s value has skyrocketed.

“It has been independently appraised at $5 million and it wouldn’t surprise me if we have an offer in that neighborhood in the next couple of days,” David McCarthy, a senior numismatist at Kagin’s, told The Washington Post.

A second photo of Billy the Kid, a 2 x 3-inch tintype portrait taken in 1880 and sold in 2010, went for $2.3 million, according to Kagin’s.

McCarthy noted that the company has already been contacted by three potential buyers about the newest photographic find.

In a statement posted on the company’s Web site, he said the company’s experts were “understandably skeptical” when the photo of Kid surfaced.

“An original Billy the Kid photo is the holy grail of Western Americana,” he said. “We had to be certain that we could answer and verify where, when, how and why this photograph was taken. Simple resemblance is not enough in a case like this – a team of experts had to be assembled to address each and every detail in the photo to ensure that nothing was out of place.”

[Billy the Kid’s former hideout is on the market, and it’s adorably charming]

The full tintype photograph shows notorious outlaw Billy the Kid alongside members of his gang after a wedding in the summer of 1878. (Courtesy of Kagin’s)

The latest photo, a 4 x 5 inch tintype, captures Billy the Kid surrounded by several members of his gang after a wedding, according to Kagin’s. The outlaws are surrounded by friends and family in Chaves County, N.M., in the summer of 1878. The company said a team spent a year dissecting the photo and determining the location, which required investigators to travel to the supposed site where it was taken.

“We found the old lumber underneath,” Jeff Aiello, who directed a National Geographic Channel documentary about the photo, told ABC affiliate KFSN. “We found those exact rock piers are still there.”

According to the company:

Taken just one month after the tumultuous Lincoln County War came to an end, it is a window into the lives of these gunmen as they were still fighting the injustices of a lawless land.  It’s a carefree moment after an important life event – a wedding – which is rich in content, movement and texture.

Aiello told KFSN that the photo is particularly significant because it’s the only known photo of Billy the Kid with his gang, The Regulators, making it a unique piece of American history.

“Like Don Kagin said, it’s the holy grail of not just western photography, it’s the holy grail of photography,” Aiello told KFSN. “It is the rarest photograph in the world and it was found in a Fresno junk shop.”

Legend holds that Billy the Kid was responsible for 21 deaths, one for each year of his life, according to CBS. The New Mexico Tourism Department, however, claims the number is probably less than half that many.

Croquet, now considered a posh British pastime, may appear to be an unlikely sport for a ruthless outlaw, but Liz Larsson from the U.K.’s Croquet Association, told the Guardian that the sport had swept the United States years earlier.

“Croquet became popular in the 1860s because it was the first sport that women could play on the same terms as men, and men and women could play each other,” she said. “It had a huge boost in its popularity.”

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