What could be a World War II era recipe for Coca-Cola's secret formula found a buyer on eBay — a 15-year-old who now has three days to come up with $15 million to pay for it.

Georgia antiques dealer Cliff Kluge listed the yellowing typewritten document — found among papers at a Tennessee estate sale — with an opening bid of $5 million and a buy-it-now price of $15 million as a publicity stunt.

"It would have been a wonderful thing" if it had found a genuine buyer, Kluge told AFP by telephone, "but some 15-year-old kid bid on it (at $15 million) — and it's not a legitimate bid."

Undaunted, Kluge said he will relist it after a three-day waiting period, required under eBay rules, on the off-chance that the adolescent buyer can somehow rustle up the cash.

"I wanted to draw attention to it, which worked," said Kluge when asked why he listed the document, dated January 1943, on the popular online auction website.

Coca-Cola, which traces its origins to a 19th century patent medicine, says its formula of natural ingredients is a closely-held trade secret, kept in a vault at its World of Coca-Cola museum in Atlanta.

"We sleep well at night knowing the secret formula is safe and secure with us," Coca-Cola spokesman Petro Kacur told AFP.

Kluge, whose copy is in a safety deposit box, acknowledged: "I can't prove this is the original recipe. No one can because only two people (both executives of Coca-Cola) in the world know it."

In 2011 the public radio show "This American Life" came out with what it believed to be a handwritten original recipe for Coca-Cola, which in its earliest form had cocaine among its ingredients.