An X-acto blade can slit a page from a book in less than a second, and police say that's how a well-known rare-documents dealer stole maps worth hundreds of thousands of dollars from Yale University.

The Philadelphia-based FBI art crime team issued an alert this month to institutions that hold rare maps in their collections, advising them to determine whether they were missing any, and soon libraries from Chicago to London were reporting that they were. No rare maps in local collections are missing, but those in charge of reading rooms say that such major thefts always prompt reviews of inventory and security measures.

E. Forbes Smiley III, a Masschusetts-based dealer in antique maps, has been charged with stealing rare maps by cutting them from books in Yale University's Beinecke Rare Book and Manuscript Library. A librarian spotted a blade on the floor of the reading room this summer. A Yale detective followed Smiley out of the library and asked if the blade belonged to him.

According to an affidavit filed in Connecticut Superior Court, Smiley replied, "Yes, it is. I must have dropped it," and then, inexplicably, added, "I have a cold."

In Smiley's briefcase and pockets, the detective found several rare maps, together valued at $878,000. He pleaded not guilty last week and is due back in court Oct. 3.

This isn't the first case of rare-book slasher thefts. A former landscape gardener named Peter Bellwood systematically and repeatedly pillaged the National Library of Wales over a period of months in 2000 by cutting maps out of books with a hobby knife and sticking them down his pants.

But the notion that an act more associated with thoughtless college students than savvy thieves could allow theft of rare and valuable items has roiled the community of scholars and collectors bound together by their fascination with maps.

Maps tucked into books are especially vulnerable, said Tony Campbell, former map librarian at the British Library who also worked as an antiquarian map dealer.

"If you take a page out of a rare book, you've got a worthless piece of paper. But if you take a map, you haven't destroyed its worth. It's likely to have fair amount of value, and it's virtually untraceable. That's the joy of it for the thief."

The theft can be hard to detect. "That book is handed to someone, then handed back with one folded map removed," Campbell said.

Unless the librarian is aware that there are maps inside the book, and knows how many, a theft can easily go undetected.

"Now all the libraries, not just in North America, are scurrying around, scrabbling about, looking to see whether those books lost their maps," Campbell said.

The FBI art crime team is investigating whether Smiley has taken maps from the Newberry Library in Chicago, the British Library in London and the Boston Public Library. There is no indication that Smiley visited any Pittsburgh libraries.

The fact that thefts can go undetected for years is one of the aspects of this type of crime that makes it difficult to fight. It might seem basic that a library should know what it has and whether something is missing, but it's not that simple.

"We have about 30,000 boxes of archival materials. That's excluding the thousands of books we have," said Michael Dabrishus, assistant director of libraries for archives, special collections and preservation at the University of Pittsburgh. "Even within a box, there may be [up to] 3,000 pieces of paper or other items. Trying to do inventory would be quite time consuming."

Much mitigates against preventing theft or catching map thieves, Campbell said.

Knowledgeable thieves can take what he calls "common rare maps," documents with a number of copies around the world, some of which could legitimately be for sale. "How's anyone going to know which is legitimate and which are not?"

Dealers or buyers would know whether libraries marked such documents with indelible stamps of some kind, a practice Campbell advocates but which many others in the field do not like.

"I know some institutions that did emboss valuable materials, but anything that is done that might somehow damage or mar an item is frowned upon in this business, particularly with rare maps or rare manuscripts," Dabrishus said. "We're caught, on one hand, trying to provide access to these materials and, on the other hand, most collectors don't like to collect something like that. People out there collecting want the most pristine copy available."

Things are different at Carnegie Library, which didn't have a special collections section until 1988, archivist Greg Priore said.

"Most of the material in the library has been stamped to death," said Priore, who is in charge of the Carnegie's William R. Oliver Special Collections Room.

Ink or perforated stamps are on many maps, he said. "From a rarity standpoint, that hurts it" and makes those such as himself who care about documents cringe, "but from a security standpoint, it makes it hard to pass something off."

The clubby nature of the field also has made some institutions reluctant to take security measures, such as forcing people to check coats and bags, sign in and out, give proof of identity, or submit to searches, Campbell said.

"It was sort of a gentlemen's club of scholars and respected dealers. It seemed to be, somehow, not the way one went about things."

Though many libraries, including Yale's, use security systems with closed-circuit television, "some are loath to. Researchers don't like to think of Big Brother looking over them," Dabrishus said.

Even with such measures, Campbell said, there might be a tendency to let well-known patrons slide. Smiley had been a suspect in a previous theft, but there was no alert about him passed to other institutions. That's a mistake that a number of theft cases make clear.

One of the best-known map thieves is Gilbert Bland Jr., a rare-maps dealer from Tamarac, Fla., who pilfered from at least 19 institutions in the early 1990s. He took maps that the FBI valued at about $500,000 before being caught fleeing the Peabody Library of Johns Hopkins University in 1995 with three maps, a phony university ID card and a notebook with a list of rare maps and the major libraries that had them in their collections. Police initially let him go and had to track him down later.

Victims sometimes are reluctant to reveal the crimes or to share information about them, Campbell said. Secrecy has made pursuing thieves harder.

"Institutions are worried about political embarrassment and the fear that publicity will encourage further thefts," he wrote in an essay on the topic.

After Bland was caught and the stolen maps recovered, "There was a warehouse of stuff, and word went out to come get it," Campbell said. Almost no institutions showed up because, "either they didn't know [that they had lost items] or didn't come forward because it would be acknowledging that they lost them."

Some law enforcement agencies also urge secrecy, Campbell said, "believing that it is easier to catch a thief if he is unaware that the loss has been discovered."

The secrecy is often misguided, he said. Dealers need to know immediately what stolen items are out there that might be offered to them. Other libraries and archives need to know that they might have been robbed or could be robbed. Police in other jurisdictions need to know the pattern of thefts so they can be aware.

Not spreading the word of a theft also prevents investigators and others from noticing patterns or anomalies that might help them prevent theft or catch thieves.

Those in charge of local rare-document collections said they believed the measures they have in place are effective. All said they had had no significant thefts in recent years.

Dabrishus did not want to supply details of the security at collections he supervises, the Darlington Memorial Library, the Special Collections Department in Hillman Library, the Archive Service Center, the Stephen Foster Memorial Library and some small department collections, but he said most major institutions used electronic surveillance, required patrons to check bags and coats, and searched bags when patrons leave.

Human monitoring of patrons is probably still the main way of deterring theft. Priore said he keeps a close eye on people using rare materials.

"It's not far at all from where they sit to where I sit. I'm almost on top of them. I do not let people go down the stacks. People are never left unattended. Things are not brought out of this room. And I check things when I put them back."

Many of the 25,000 or so items in the special collections have greater historic and research value than monetary value, he said. But the library does have some gems, a collection of photos of North American Eskimos by Edward Curtis, and a music manuscript with Johann Sebastian Bach's handwriting on it.

Similarly, the Senator John Heinz Pittsburgh Regional History Museum has mostly items of local historical interest, said Betty Arenth, senior vice president and the head of security. There are valuable items, and everything is available to scholars.

"For the most valuable things, we use facsimiles. If there is a valuable original that a person needs to examine, they are accompanied. We bring the original out to the reader and sit with them," Arenth said. The item or items are checked after the reader is done.

Thefts over the years make it clear that such security is needed, even when scholars, librarians and dealers feel that they are friends and colleagues who share a common love.

It's painful to see the results of "someone mutilating a book to take something out of it," Priore said.