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An Italian expert in Hebrew manuscripts said Wednesday he had discovered the oldest known complete Torah scroll, a sheepskin document dating from 1155-1225. It was right under his nose, in the University of Bologna library, where it had been mistakenly catalogued a century ago as dating from the 17th century.

The find isn't the oldest Torah text in the world: Both the Leningrad and the Aleppo bibles — both of them Hebrew codexes, or books — pre-date the Bologna scroll by more than 200 years. But this is the oldest Torah scroll of the Pentateuch, the first five books of Moses, according to Mauro Perani, a professor of Hebrew in the University of Bologna's cultural heritage department.

Such scrolls — this one is 36 meters (40 yards) long and 64 centimeters (25 inches) high — are brought out in synagogues on the Sabbath and holidays and portions are read aloud in public.

Perani was updating the library's Hebrew manuscript catalogue when he stumbled upon the scroll in February. In a telephone interview Wednesday, Perani said he immediately recognized the scroll had been wrongly dated when the last catalogue was completed in 1889, because he recognized that its script and other graphic notations were far older.

He said it was "completely normal" for such mistakes to have been made in the late 1800s, given the "science of manuscripts was not yet born."

Two separate carbon-dating tests, performed by the University of Salento in Italy and the Radiocarbon Dating Laboratory at the University of Illinois, Urbana-Champaign, confirmed the revised dating, according to a statement from the University of Bologna.

Outside experts said the finding was important even though older Hebrew bibles do exist.

"It is fairly big news," said James Aiken, a lecturer in Hebrew and Old Testament studies at Cambridge University. "Hebrew scholars get excited by very small things, but it certainly is important and clearly looks like a very beautiful scroll."

Giovanni Garbini, a leading expert on ancient Semitic languages and retired professor at Rome's La Sapienza university, however, said the discovery doesn't change much about what the world knows about Hebrew manuscripts.

"It's an example of an ancient scroll, but from the point of view of knowledge, it doesn't change anything," he said in a phone interview.