A newly-analyzed photo purportedly shows Robert Johnson, the mysterious blues legend whose meager recordings became a groundwork for American popular music.

Only two such photos have been unequivocally confirmed, and the prospect of another is held as a holy grail in blues society.

Johnson was an influential early blues singer and guitarist whose songs have been covered by the likes of The Rolling Stones, Eric Clapton, Led Zeppelin, The White Stripes, Fleetwood Mac and countless others. He also infamously is alleged to have made a deal with the devil, who personally tuned Johnson's guitar at a crossroads in Mississippi, thus giving him his extraordinary guitar skills in exchange for his soul.

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He wandered the South and earned acclaim picking guitar tunes, but he made just two recordings—in San Antonio in 1936 and in Dallas in 1937.

The identification comes from Lois Gibson, award-winning forensic artist for the Houston Police Department and professional analyst of historical photographs. She also announced identification of a Johnson photo in 2008; that one was accepted by the Johnson estate but widely contested by blues historians.

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The new photograph turned up in an antique Winthrop desk, filled with odds and ends, bought in a 2013 auction by Donald Roark, a 64-year-old retired lawyer and professor in Pensacola, Florida.

In a cluttered draw was a three-by-five inch photo of four people seated at a public table, the man in question on the left.

"I guess it was because of the hat," Roark said, recalling his first glimpse of the picture, and his memory of the photo cover of the Robert Johnson album he owns. "I chuckled and thought that guy kind of looks like Robert Johnson."

When he asked his wife who the man looked like, she said Robert Johnson. He sat on the suspicion for two years, until reaching out to Gibson's manager online for a professional take on the photograph.

It was one of the five-or-so requests for a photo identification Gibson gets each month, she said.

"Ninety-nine percent of them I look at and well, I don't laugh in their face, but I shrug it off," she said.

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But the purported Johnson photo gave her pause. Gibson, who spent the last three decades analyzing and reconstructing faces, said she recognized Johnson's face. But the scene offered further evidence—three people who Gibson identified as known acquaintances of Johnson: Calletta Craft, Johnson's wife from 1931, who bears a marked eye condition; Estella Coleman, who housed Johnson since 1933; and her son Robert Lockwood Jr.

That crowd would set the purported image in the mid 1930s, before Johnson made a name as a nomadic guitar player and blues singer, and before was afforded the privilege to record.

Two years after his first session, Johnson died in 1938 at age 27 (making him the first great musician in the notable company of the "27 Club," alongside Brian Jones, Jimi Hendrix, Janis Joplin, Jim Morrison and Kurt Cobain).

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But his enduring sound, captured in Texas studios, helped motivate music for decades to come with its eerie invocations of the devil. His sound famously inspired the young ensemble that would become the Rolling Stones. The Washington Post reported in 2011 there are 30 records with at least one cover of a Johnson song on them that have sold more than a million copies.

Because of Johnson's mysterious legacy, blues scholars are eternally skeptical of the emergence of new photos. A May 2015 article in Texas Monthly evoked a purported Johnson image—confirmed as the image currently in question–which scholars swiftly dismissed.

But Gibson, who won a Guiness World Record for most successful forensic artist, said that historical scholars are not qualified to make those assertions about photographs.

"These blues people are not specialists in facial structure. I am," she said. "They would not know a superciliary arch from a philtrum."

With only two sure photos of Johnson, shot in studio and documented at the time, a broad consensus on the authenticity of the newly-surfaced photo is unlikely.