Fifty-four years after it was sold by looters, an ancient Maya pictographic text was judged authentic by scholars Thursday.

Mexico's National Institute of History and Anthropology said the calendar-style text was made between 1021 and 1154 A.D. and is the oldest known pre-Hispanic document.

The 10 surviving pages of the tree-bark folding "book" will now be known as the Mexico Maya Codex. It had been known as the Grolier Codex. It may have originally had 20 pages, but some were lost after centuries in a cave in southern Chiapas state.

It contains a series of observations and predictions related to the astral movement of Venus. Mayan texts are written in a series of syllabic glyphs, in which a stylized painted figure often stands for a syllable.

A Mexican collector bought it in 1964, and it was first exhibited at the Grolier Club in New York in 1971.

Collector Josue Saenz returned the book to Mexican authorities in 1974.

The fact that it was looted and had a simpler design than other surviving texts had led some to doubt its authenticity.

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