The purported signature of Donald Trump on a Bible that sold recently on eBay for $325 is fake, three authenticators said Wednesday.

The sale generated headlines after the president was seen signing Bibles earlier this month as he toured tornado damage in Alabama. Cameras snapped as Trump signed the Bible of a fifth-grader and posed for a photo with him.

The eBay listing claimed the Bible for sale was signed by Trump in 2016 before his inauguration.

The sale caught the eye of eBay seller David Flores, an Orange County, California, resident who found the item strange because, he said, the signature looked wrong and because "you weren’t hearing about him signing Bibles in 2016."

Justin Steffman, the CEO and lead authenticator of AutographCOA.com, examined photos of the Bible and its signature and quickly concluded that the autograph was counterfeit.

"I have taken a close look and compared the book to our authentic exemplar database," Steffman said by email. "The signature on the Bible definitely does not appear to be an authentic signature from President Trump. The odds of it being real are zero percent in my opinion."

Two authenticators from the firm PSA/DNA, principal authenticator Kevin Keating and Florida-based Tom Poon, separately came to the same conclusion based on photographs of the endorsement.

"Both of them came back almost immediately with thumbs down," said Terry Melia, spokesman for the company.

Those findings were not surprising, Melia said.

"The percentage of fake autographs being sold on eBay — ones that do not already include third-party authentication behind them — is easily 50 percent or more," he said in an email.

The Bible allegedly signed by Trump came with a certificate of authenticity, the listing said. The seller stated that it "obtains all our memorabilia and autographs in person directly from the celebrity signers themselves."

The seller responded through eBay's messaging system to questions from NBC News about the listing: "Do not contact me again or I will contact my lawyer and get you for harassment."

Ryan Moore, an eBay spokesman, said by email, "Our policies require that items listed on eBay are authentic. In the rare case a buyer believes they have purchased an item that is inauthentic, eBay’s Money Back Guarantee will cover them."

The site's autograph policy does not say eBay requires authenticity, but it does say that it employ's third-party authenticators who "may" evaluate a listing if a complaint is lodged. "If they have concerns about an item’s authenticity, eBay may remove the listing from the site," the policy states.

Craig Crosby, founder of The Counterfeit Report, a website backed by a range of consumer brands concerned about sales of fakes, alleges eBay and other sites have long been havens for bogus celebrity signatures.

He said until the platforms are held directly liable for the sale of items with counterfeit signatures, they'll continue to facilitate them because "it's a substantial money maker for them."

President Donald Trump signs a Bible as he greets people at Providence Baptist Church in Smiths Station, Alabama, on March 8, 2019, while touring areas where tornadoes killed 23 people in Lee County. Carolyn Kaster / AP

Crosby said he counted 598 items with Trump's signature for sale on eBay Wednesday afternoon.

Steffman of AutographCOA said items containing the president's endorsement are popular among fans and collectors.

"The high value of Trump's autograph and his heart rate monitor-style signature make him one of the most faked autographs on the market," he said by email. "The percentage of fake Trump autographs for sale on eBay is much higher than authentic signatures, without a doubt."

Experts and eBay agree that buyers should seek items with a certificate or letter of authenticity from a known authenticator.

Flores said that as long as there are people willing to buy unverified autographs, they'll be available. And sellers simply close up shop when they're found out, only to crop up under a new name, he said.

"It’s a little bit like the Wild West in that way," Flores said of the counterfeit market online. "You can sell fake autographs and not get caught every time."