The old letter contained an obscure Army officer's report about bandits on the California frontier in the winter of 1861. It was the signature at the end that grabbed the attention of Wayne E. Motts.

The three-page, handwritten document was signed by Lewis A. Armistead, then a lowly U.S. Army officer, but later the Confederate general who died leading a famous doomed charge in the Battle of Gettysburg. Motts knew that the letter, which was being offered for sale on eBay, was rare. Few "Armisteads" reached the collectors' market.

He knew that letter particularly well. Ten years earlier, he examined it himself -- at the National Archives in Washington. And he knew there was only one way it could be offered on eBay: It had been stolen.

Motts's realization one night last year, as he sat at his computer in his home outside Gettysburg, Pa., sparked an investigation that led to the discovery of scores of stolen archives documents and the conviction of a reclusive Virginia researcher who was sentenced to prison last month for taking them.

The thefts sent a wave of anxiety through the nation's beleaguered historical repositories, as well as the usually staid but often high-stakes market in which historical documents are bought and sold.

Motts, 38, the director of Gettysburg's Adams County Historical Society, is scheduled to be honored at the National Archives today for alerting authorities to the pilfered Armistead letter.

Howard Harner, 68, a relic hunter and collector from Staunton who admitted to stealing more than 100 documents and selling many of them, was sentenced last month to two years in prison. He pleaded guilty in March.

Harner, a history buff since the 1960s, said in a telephone interview last week that his stealing occurred over the past few years. "My problem is of recent vintage," he said. And though investigators said he netted more than $47,000, he said money wasn't the object at first.

"It wasn't initiated that way," he said. "It was the interest in the individual composition, and [the author's] importance later on during the Civil War. It began that way, then economic necessity forced disposal gradually."

Harner is believed to have taken the documents between 1996 and 2002, said Paul Brachfeld, the archives inspector general. Harner might have taken more than the authorities know, Brachfeld said last week. Only 42 documents have been recovered. Investigators are trying to track the rest, some of which might be in the hands of collectors who don't know the documents are stolen.

Harner, who hid the papers in his clothing while researching in the archives' downtown Washington headquarters, took letters signed by such figures as Confederate Gen. Robert E. Lee, Confederate President Jefferson Davis and Union generals Ulysses S. Grant and George A. Custer.

But authorities said he also stole documents bearing the less well-known but still highly marketable signatures of such people as Armistead and the Confederate generals George Pickett and Ambrose P. Hill.

Brachfeld said the National Archives, which has since beefed up its security, does not keep an "item level" inventory of everything in its holdings. "It's not like a car dealership, where you arrive in the morning and you notice a car's missing from the lot," he said.

Brachfeld said that in several cases, Harner appears to have cut the signatures off the documents and sold the signatures by themselves to autograph collectors. Harner sold many of his documents to a reputable collector in nearby Lexington, according to authorities, and others to a prominent auction house and individuals.

Those buyers often resold them to others who then sold them again. Often, the price went up with each sale. In some cases, the item's value more than doubled, and in a few cases the items were purchased by aficionados with extensive collections who paid top dollar.

Another letter written by Armistead, in which he resigned from the Army to join the Confederates, was purchased five years ago for $40,000 by the Pearce Collections at Navarro College, outside Dallas. The college bought it from a dealer in California, and authorities indicated that Harner originally sold it for $18,000 to Jim Putbrese, the collector in Lexington.

The letter has been returned to the archives, and the college was reimbursed by the seller, said Darrell Beauchamp, the school's dean of libraries and special collections.

Two other valuable letters, one from Pickett and another from Confederate Gen. Richard B. Garnett, were purchased for $20,000 each by John L. Nau III, a wealthy Houston collector and University of Virginia benefactor.

"I applaud the federal authorities for taking the firm action as quickly as they did," said Nau, who chairs the federal government's Advisory Council on Historic Preservation. "The fact that the authorities, when given information, will immediately act on it, that's the good news. The bad news is, we've got people that will steal" such things.

Nau said he returned the letters to the archives and was reimbursed in full by Putbrese, who had sold him the letters.

Putbrese, the original buyer of many Harner documents, said in a telephone interview that he had known Harner for about four years.

He described Harner as a smart, intense and reclusive researcher who once grew his beard down to his waist, haunted Civil War sites with a metal detector and worked at home at a table cluttered with maps and papers. "The guy looked like he was from 100 years ago," Putbrese said.

Putbrese said that he helped investigators locate many of the stolen documents and that he has reimbursed everyone who bought a document from him. As "the last one in line," he said he is seeking reimbursement from Harner, who has offered him antiques as restitution.

He said Harner, in the past, sold antique firearms and was well-known in collector circles as eccentric but upstanding.

"Whenever he needed money, I would get a call from him and he would have a document for sale," Putbrese said.

Investigators said last week that Harner's thefts probably would have continued had it not been for the fascination Motts has with the tragic life of Armistead.

"I could not believe it," Motts said when he realized the general's letter was stolen. "I just could not accept it. To me . . . it's sort of like the ultimate sin to take the historic document. It's there for public view."

Gettysburg historian Wayne E. Motts will be honored at the National Archives for alerting authorities to a stolen 1861 military letter he spotted on eBay.