Two experts in historical documents say they doubt the authenticity of a Davy Crockett letter that the Texas Historical Commission bought this week for nearly half a million dollars.

Both questioned the handwriting in the document, dated Jan. 9, 1836, and one said the grammar was just too good to belong to the Alamo defender.

"The letter has better grammar, better punctuation than Davy Crockett had ever used," said Kevin MacDonnell, a seller of antique books in Austin.

Everett Wilke, a private appraiser of historical manuscripts based in Bluffton, said he compared the handwriting with that in known Crockett letters owned by East Carolina University.

"Those are genuine Crockett letters, and it (the letter purchased by the state) don't look a thing like them," Wilke said. "It's not that difficult to tell it's not real."

The Texas Historical Commission announced Tuesday that it was acquiring the letter from Houston-based Simpson Galleries of $490,000. The document is believed to be the last letter Crockett wrote before he and other Alamo defenders were killed by Mexican forces.

The letter has yet to be authenticated, but Historical Commission spokeswoman Debbi Head said she is "99.9 percent sure" it is real.

The $490,000 the state paid will be held in an escrow account pending the outcome of a third-party investigation, Head said. The state has 120 days to complete the authentication.

Wilke, who has been studying and appraising Americana manuscripts for 30 years, said the signature on the letter is different than Crockett's signature on other documents. The "k" in Crockett on the East Carolina University letters doesn't match the Texas letter, he said.

MacDonnell also expressed doubts about the handwriting, as well as the accuracy of the spelling and grammar. He suggested the letter was probably meant to be a true copy made for reference purposes rather than a hoax.

"The copyist or scrivener probably cleaned up the writing on the letter when he was copying it," MacDonnell said.

Ray Simpson III of Houston, the letter's seller, said he hadn't heard any doubts about the letter's authenticity.

"I am very positive that this is the original Davy Crockett letter," he said. "We do think it's right, and we do think it will be proven through the state's third-party investigation."