A photograph of Wild West outlaw Billy the Kid has sold for a king’s ransom at auction. Energy tycoon William Koch purchased the above portrait of William Bonney — the only one known in existence — for $2.3 million, almost 5 times the expected amount.

Koch, billionaire founder and president of the energy development holding company Oxbow Group, was the iconic photo’s winning bidder at the Brian Lebel Old West Show & Auction in Colorado. The $2.3 million price tag for the tintype photo is well over the expected bid of $300,000 to $400,000.

Other than perhaps Jesse James, Billy the Kid is arguably the most famous criminal of the Old West during the latter part of the 19th century. Alleged to have killed 21 people (though it was probably considerably less), the Kid’s legendary bank-robbing and gun-slinging escapades have made him a cult folk hero in the 130 years following his death at the hands of sheriff Pat Garret in 1881.

In this iconic portrait (thought to have been taken in early 1880), the outlaw is shown with a Winchester carbine at his side and a Colt revolver stuck in his holster. The Kid himself gave the image to his cattle-rustling partner, Dan Dedrick, who later passed the photograph down to his family.

Also called melainotype and ferrotype, tintype is a photographic process similar to ambrotype, in which an image’s direct positive is created on a sheet of glass. Tintype, however, uses metal instead of glass.