A librarian in Saint Omer, Northern France, has stumbled upon a 1623 copy of William Shakespeare’s First Folio, AFP reports. Remy Cordonnier found the rare compilation of the Bard of Avon’s plays while preparing books for an exhibition on English literature.

“It occurred to me that it could be an unidentified First Folio, with historic importance and great intellectual value,” he told AFP.

The book has now been authenticated by one of the world’s leading Shakespeare experts, Eric Rasmussen of the University of Nevada, who said it had been 10 years since a new copy had been discovered.

He told AFP that the printed text was “immediately identifiable,” thanks to recognizable features such as unique markings, paper weight, and a series of errors found only in this particular edition.

Although books of such scarcity fetch top prices, the Saint Omer copy has several flaws, including missing title pages, heavy annotations, and the absence of the entire play The Two Gentleman of Verona.

Assessing the damage, library director Francoise Ducroquet estimated that the book would likely be worth substantially less that the €2.5 – €5 million other volumes of the First Folio have achieved at auction.

Of an estimated original print run of 750, only 233 copies of the First Folio have survived.