Deep in a vault in Mexico City’s Museo Nacional​ de Antropología sits a manuscript that has long been shrouded in controversy. Said to have been found in a Mexican cave in a box along with a turquoise mask, the manuscript contains 11 pages of paper covered with images of pre-Columbian death gods and Maya iconography. But because it was discovered by looters, its origins have been mistrusted by scholars, until now. As Fine Books & Collections reports, scientists now believe that the 13th-century codex is the real deal.

The codex has long been called the “Grolier Codex” because it was displayed at the Grolier Club, a members-only institution in New York that caters to fine book and graphic design lovers. But that exhibition—and the fact that its owner chose to display it there instead of repatriating it to Mexico—is part of a long series of doubts about the manuscript.

The trouble started when the Josué Sáenz, a wealthy Mexican collector, was flown to an undisclosed location in what he characterized as a cold call by looters who had discovered the codex and other treasures in a cave, Fine Books & Collections reports. Sáenz ended up buying the codex and displayed it at the Grolier Club instead of keeping it in Mexico. This, plus the fact that the manuscript was different from other, authenticated papers, fueled suspicions that it was a fake.

Now, a group of archaeologists, anthropologists and cultural experts have declared the find real in a paper published in a special edition of the journal Maya Archaeology. After reviewing the research, studying the codex itself and analyzing everything from its paper to the sketches that lie beneath its drawings, they concluded it is genuine.

“Our goal was to see if there was something that was modern that [may] have been put into the paint on the Codex…to confirm that it was a 20th century fraud,” Yale art historian Mary Miller, who collaborated on the paper, tells PRI. But their review of recent research, which includes a study that used everything from X-rays to UV imaging and microscopic analysis, points to its authenticity. As Ben Guarino reports for The Washington Post, the team thinks the codex was written in 1230 and that its existence is “nothing less than a miracle.”

As such, it is the oldest book of the Americas—appropriate to a culture that stood mighty among those original to Mesoamerica. The Maya civilization produced spectacular science, math, calendars, archaeology and cultural treasures between 2,000 B.C. and the Spanish incursion of 1697, and more than 7 million Maya still live in Mesoamerica today.

That cultural heritage has long intrigued historians and archaeologists, who prize other codices housed in Dresden, Madrid and Paris. And with the revelation that the Grolier Codex is real, researchers can get to work analyzing the ornate illustrations and what they could mean about Maya religion and life.

This news comes on the heels of the recent unveiling of a slew of hidden images in the Codex Selden, a Mixtec manuscript donated to the Bodleian Libraries in the 1600s. The heights of the Maya and Mixtec civilizations may be behind us, but it’s still a golden age for the manuscripts they left behind.

Update September 20, 2017: The date for the discovery of the Codex Selden has been corrected to show that the manuscript has been in the Bodleian Libraries since the 17th century.