An archivist and an antique bookseller were charged Friday with stealing millions of dollars’ worth of rare books, illustrations, maps and photographs from a Pennsylvania library over a 20-year period, including Isaac Newton’s “Principia,” considered a watershed of science.

Greg Priore, the former archivist at the Carnegie Library of Pittsburgh, appears at his arraignment Friday in Pittsburgh. Darrell Sapp/Pittsburgh Post-Gazette via Associated Press

In some cases, the archivist used an X-Acto knife to cut potentially valuable maps and illustrations out of books in the Carnegie Library of Pittsburgh’s historical collection, authorities said. They ultimately sold to other collectors famous originals that were hundreds of years old, authorities said.

Researchers found more than 300 items damaged or missing, a loss estimated at $8 million.

Former Carnegie Library archivist Gregory Priore, 61, and bookstore owner John Schulman, 54, were charged with theft, conspiracy, forgery, receiving stolen property and other counts in the disappearance of hundreds of items.

In a statement, library officials said they were “deeply disappointed that at the center of this case are two people who had close, long-standing relationships with the library.”

Some in the antique and historical book world had heard about the case in the spring when authorities issued a detailed list of missing items and then when authorities unsealed search warrants three weeks ago.

Ellen Dunlap, president of the American Antiquarian Society, said institutions, booksellers and collectors likely are going through their records to determine whether they bought or resold anything from Schulman’s store, Caliban Book Shop.

“I can assure you if anybody bought anything from Caliban, they’re seeing these headlines and saying, ‘Uh oh, I’m looking at my books right now,”‘ Dunlap said.

The alleged scheme started unraveling last year when appraisers began a routine audit commissioned by the library and discovered that items were missing or damaged since the last audit in 1991.

The library locked down the room, and appraisers quickly began finding missing items for sale online, as well as items that had been sold or advertised by Schulman’s bookstore, a block away from the library.

In June 2017, library officials contacted authorities and fired Priore.

Detectives say efforts to recover the items have netted books, plates and maps estimated at a value of $1.1 million. Some were found during a search last year of Schulman’s book warehouse, detectives said.

One particularly valuable item allegedly stolen and recovered was Newton’s “Philosophiae Naturalis Principia Mathematica,” with an estimated value of $900,000.

Caliban Book Shop co-owner John Schulman leaves after his arraignment at City Court on Friday in Pittsburgh. Authorities on Friday charged Schulman and Greg Priore, a Carnegie Library archivist, with stealing millions of dollars’ worth of rare books, illustrations, maps and photographs from a Pittsburgh library over a 20-year period. Darrell Sapp/Pittsburgh Post-Gazette via Associated Press

Listed as a total loss are: “An Inquiry into the Nature and Causes of the Wealth of Nations” by Adam Smith, at a value of $180,000; a journal of George Washington, estimated at $250,000; and “Reise in das Innere Nord-America” by Prince Alexander Philipp Maximilian and Karl Bodmer, at a value of $1.2 million.

In one case, the men allegedly forged a letter from the library to help them sell a book signed by Thomas Jefferson. The letter was designed to make it look as though the library had removed the book from its archives, detectives said.

An appraiser helping detectives found that book, “De la France et des Etats-Unis,” for sale online for $95,000 from a bookstore in New York. The book had been bought and sold twice after Schulman allegedly sold it to Bartleby’s, detectives said.

In a 36-page narrative filed in court, Priore told detectives that he first approached Schulman in the late 1990s about selling items from the library’s special collection and that Schulman agreed to do it.

Priore, who in 1991 became manager and archivist of the library’s special collections room, simply walked out of the library with books, authorities say.

Sometimes Priore concealed maps or illustrations in a manila folder or, if it was larger, rolled it up and carried it out, they said.

Schulman paid Priore up front and pocketed the cash from items he could unload, detectives said.