One collector got more than he bargained for at a Fresno junk shop.

In 2010, a man named Randy Guijarro purchased a rare photo of legendary outlaw Billy the Kid as part of a miscellaneous lot. Now, the image could get him as much as $5 million.

In the photo the outlaw can be seen playing croquet with his gang of Lincoln County Regulators in the summer of 1878. Americana company Kagin’s, which is negotiating the sale of the photo, says it’s basing its estimate of the 4-by-5-inch tintype image on the sale of the only other known photo of Billy the Kid, which went for $2.3 million.

“When we first saw the photograph, we were understandably skeptical—an original Billy the Kid photo is the Holy Grail of Western Americana,” Kagin’s David McCarthy told The New York Post.

“We had to be sure 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 insure that nothing was out of place.”

The National Geographic Channel will air a Kevin Costner-narrated special detailing the backstory of the photo Sunday at 9 p.m., called “Billy the Kid: New Evidence.”