ABC News' Steve Osunsami reports:

A Georgia man believes he has found a copy of the recipe for Coca-Cola and is trying to sell the top-secret document on eBay for at least $5 million.

Cliff Kluge, a pilot, and his wife Arlene of Ringgold, Ga., said they purchased several old boxes of papers and letters at an estate sale around four years ago for about $100. In the box of letters, the couple stumbled upon a 1943 recipe with references to one of the most popular soft drinks in the world today.

"When I saw this I just thought it was interesting, so I folded it up, stuck it in my purse and carried it around for a couple of weeks showing my friends," Arlene Kluge, a small business owner, told ABC News.

Taking no chances, the couple eventually put the recipe in a safety deposit box. After thinking about it for a while, they thought they were sitting on the recipe for Coca-Cola.

"Whoever had typed this letter had seen the original recipe," Cliff Kluge said. "The letter always references Coke and products and stuff.

"We believe it is definitely related to Coca-Cola," he added.

Kluge has put the formula on eBay with a starting bid of $5 million. If you're not one to play the bidding game, you can simply use the "buy it now" option and the recipe is yours for $15 million. No one has attempted to put a bid down and the auction ends later today.

Kluge showed ABC News a copy of the document with the important ingredients blocked out. He reached out to Coca-Cola when he put the recipe on eBay.

"They told me they would call me back in seven to 10 days and they never called me back," Kluge said.

For more than 100 years, the company has guarded the super-secret formula for Coke. Company officials say finding their trade secret is no different than discovering the Loch Ness Monster or Bigfoot: It's just not going to happen.

Coca-Cola did acknowledge the real recipe is located in Georgia, but not in Kluge's home. The original recipe, made in the late 19th century, is locked away in a safe at the company's headquarters in Atlanta.

"At least once a year, somebody shows up and says, 'I have the original formula for Coca-Cola. How much do you want to pay me for it?' Well, I don't need to pay them anything for it because we have the only real one," Ted Ryan, chief archivist at Coca-Cola, told ABC News.

"We know he doesn't have the formula. There is only one copy. He has what one of the many imitator copies floating around out there," he said. "So I'm going to go to sleep peacefully knowing that we still have our copy of the formula."

The real recipe for Coca-Cola is considered the Holy Grail of soda pop and Coke fanatics have been searching for the formula for years. NPR's website crashed in 2011 when it posted what it said was the secret formula.

Kluge says while he can't guarantee it's an exact replica of the original formula, he feels "pretty good" about what he found.

"There's just too many references to Coca-Cola throughout the entire recipe," he said.