Assistant professor and animator Christopher Oakley spotted Abraham Lincoln in a photo taken on the day of the Gettysburg Address. Library of Congress, Prints and Photographs Division

The world might have a second glimpse of Abraham Lincoln at Gettysburg after a professor uncovered what he says is a rare photograph of the 16th president taken the day of the Gettysburg Address, Nov. 19, 1863.

Until now, there has been only one generally accepted photograph of Lincoln that day.

In 2007, John Richter, an amateur historian and director of the Center for Civil War Photography, says he spotted the president saluting troops on a stereoscopic photograph taken 150 years ago. While historians failed to take him seriously at the time, Christopher Oakley, a former Disney animator, examined the photo earlier this year and said he found Lincoln in the photo a few yards away from where Richter initially saw him, Oakley told Smithsonian magazine.

“All I can say is I’ve sculpted Lincoln, sketched him, painted him and animated him getting shot,” he told Smithsonian. “I’ve been looking at his face for nearly 50 years, and last March, at 3 a.m. in my studio, he looked back.”

While Richter brought the photograph to light six years ago, skeptics didn’t believe it was the Great Emancipator.

“For starters, the guy on the horse looks like a Cossack. His beard is longer and much fuller than the wispy, trimmed one the president wore in his studio session with Gardner 11 days before," William Frassanito, a historian and author of "Gettysburg: A Journey in Time" told Smithsonian. "Lincoln had an unmistakable gap between his goatee and his sideburns. If you're going to spy him in a black speck in a distant background, at least get the beard right."

Oakley spotted Richter’s find when he was working on a project with students from North Carolina-Asheville University’s Virtual Lincoln Project. With the naked eye, all anyone could pick out was a tall, slim horseback rider with a beard and top hat. A white-gloved hand is raised in what appears to be a salute. While Richter carefully examined the photo using enhanced 3-D images, only when Oakley ordered the negative of the photograph from the Library of Congress did he become a believer.

"It's the best $73 I ever spent," Oakley told USA Today about purchasing the high-resolution negative of the image. "As soon as I had that in my hands, I was able to look at it much more clearly."

Using Photoshop, Oakely scanned the negative and used a separate profile shot of Lincoln taken on that day to compare the two. He overlaid the portrait shot with the photograph and made the surprising discovery.

“All the landmarks—jaw line, beard, hair, cheekbones, heavy brow, ears, line up perfectly,” Oakley said. Another key find was made by researchers. Using four photos of the Gettysburg Address, they triangulated the location of the speakers’ stand and saw that Lincoln appeared in the same spot.

While the photo has yet to be verified, Oakley says his findings can help gain new understanding on the famous Gettysburg Address.

“The historian’s job is to gather as many pieces as he can from as many sources as possible,” he said. “You come up with as logical an interpretation as you can, always realizing that new pieces will surface indefinitely.”