An old tintype photograph of a log cabin, and people in 19th century clothing. It didn't seem like much when a collector purchased the photo for two dollars at a junk shop in Fresno.

But the photo contained one of the most-wanted man in America: The gun-toting outlaw: Billy the Kid. Now that photo is worth more than $5 million.

Featured in the photo is Billy and members of his Lincoln County Regulators with croquet mallets.

Take Two's A. Martinez spoke to Donald Kagin, Western Americana dealer who appraised the photo. He says -- until now -- there was only one other authenticated photograph of Billy the Kid.

"[Billy] is in our literature, in our history and our psyche," Kagin says. "It's probably the most sought after images in Western Americana."

The lengths it took to authenticate the photo involved more than a year of investigative work. Kagan says they even had an NSA expert use facial recognition to identify members of Billy and his gang.

Other clues included combing through diary entries, and contacting New Mexico forestry officials to verify the white oak in the background.

The whole process of verifying the picture with be shown in a National Geographic Channel Documentary airing Sunday, October 18.

Correction: There was a mention in the show that the photograph was for auction at $2 million. However, the the photograph is direct to sale for $5 million. We regret the error.