"I believe the Green Foundation acted in good faith based on the information they received when they purchased the book," Matthew Morgenstern, a professor of Hebrew at Tel Aviv University, told i24news.Also, Dr. Ben Outhwaite, head of the Cambridge Genizah Research Unit, thinks it looks later than the ninth century and wants more information on how the C-14 tests were carried out. And they are not alone with their concerns. Officials from the National Library in Israel are also expressing some doubts to the AP: 'Oldest Jewish Prayer Book' Donated To Jerusalem's Bible Lands Museum. Haggai Ben Shammai, academic director of the National Library, thinks that another siddur in Germany could be the oldest, and Aviad Stollman, curator of the Judaica collection, is, like Morgenstern, skeptical both of the date and that the siddur is even a single document.
Nevertheless, there are many questions as to the book's provenance.
"No one is casting doubt that the actual pages in the book are authentic," says Morgenstern.
"But the book was written by a number of different scribes, many of the texts are incomplete and the pages are of slightly different sizes. Is what we're seeing actually a book that was bound in the Middle Ages?"
Morgenstern says it is not impossible that the ancient fragments, while genuine, could have been bound together in modern times by an antiquities dealer looking to fetch a higher price.
Background here and links.