Bruce Steiner, who describes himself as a "flea market kind of guy," stumbled across the note - written on the outside of an envelope - in October 2006 at Jamie’s Flea Market, about 30 miles west of Cleveland.

Written on the envelope was: "Let this man enter with this note. April 14, 1865," and its signature, "A. Lincoln." The date is the day the president was shot.

"I remember it was a rainy day, and this gentleman had boxes of things sitting outside," Steiner recalls. "The stuff inside the boxes were interesting, there was an old English pound note, a receipt for a carriage from the IRS dated 1863, also a JFK autograph. My guess is that all the stuff came from somebody’s estate.

"The man said he wanted $20 for anything in the box … just anything from the box was $20. I saw the old envelope and picked that, and asked him how much. He said $20 for anything in the box. He saw the signature, but he didn’t care. He just wanted $20, so I bought it.

"It was the last time I saw him, I looked for him again when I went back to the flea market, but I never saw him again."

Initially, Steiner was skeptical whether the note was "the real deal."

However, recently, Lincoln scholars from the Abraham Lincoln Presidential Library and Museum have confirmed they are "pretty sure" that the note is authentic.

"I never say I’m 100 percent sure of anything," says John Lupton, associate director with the papers of Abraham Lincoln. "But, I’m nearly as sure as possible this is authentic."

Lupton, who has spent nearly 20 years analyzing Lincoln papers, said the handwriting is "sloppy for Lincoln, which is uncharacteristic." But, after reviewing the note more closely, he now speculates the note was written hastily, or perhaps, within a moving coach.

"The signature has all the characteristics (of Lincoln’s penmanship)," he says. "What really put me over the top was the date, though. You can forge a signature, but to carry that through is very difficult … but then, you put all the pieces together. It’s contemporary paper, contemporary ink, it’s written with a steel nib pen, which Lincoln used throughout his presidency. When this is all put together, I became nearly as sure as is possible."

Of course any document with an authentic Lincoln signature is worth money; but, having a document signed on that fateful day when the President was assassinated carries quite a bit more cachet.

Because of its date, a Lincoln memorabilia dealer told the Associated Press that the note could be worth up to $25,000. Steiner says he’s not interested in selling right now, "unless some billionaire wants to trade me it for an island," he jokes.

The date is not only "key" value-wise, but also from an historical perspective.

More than any other American historian figure, Lincoln’s final day alive has been dissected and analyzed by historians. At least two movies, The Day Lincoln Was Shot (1956 and 1998) have been produced, and several books have delved into the final hours of Lincoln’s life, including the seminal book of the same name written by columnist Jim Bishop.

However, the note itself becomes a mystery. Could there had been another message inside the envelope? What were the circumstances behind the letter? The most tantalizing question is: Could it have been the last letter that Lincoln wrote, possibly as he stepped from his coach in front of Ford’s Theatre?

There are nearly 50,000 Lincoln documents within the online archive of The Papers of Abraham Lincoln. Several of those pieces were penned by Lincoln on April 14, 1865.

He wrote a short note to his Secretary of State, William H. Seward, about a meeting at 11 a.m. on that date. That day he also signed several petitions from former Confederate soldiers appealing for release from federal prisons.

History holds that the last note written by Lincoln was around 8 p.m., two hours before his assassination, scheduling a White House appointment with Congressman George Ashmun.

Similar to the Steiner letter, it was tersely worded "Allow Mr. Ashmun & friend to come in at 9:00 a.m. tomorrow," signed "A. Lincoln, April 14, 1865."

Shortly after writing the note the President and Mrs. Lincoln went out the front door of the White House, into a waiting carriage and on to Ford’s Theatre.

Whether Lincoln wrote and signed another note is purely conjecture.

"It could be Lincoln’s last signature on Earth," Steiner says. "Who knows?"

And, therein, lies the mystery.

"That date is the key element. We have it on pretty good evidence when the Ashmun letter was written," Lupton says of that note, which is housed in the Library of Congress. "But, we can’t account for each second of Lincoln’s last day … anything could have been possible - anything could have happened.

"That’s what is great about history. It’s not memorizing all the dates - it’s the detective work that makes it interesting … history is about what was really happening in the background."

Eric C. Rodenberg