Many of the unreturned pieces are 20th-century black-and-white photographs, "which is a nice balance for us," she said, since many of the society's items date from the 19th century.

In addition to the photographs are pieces of "ephemera" or memorabilia — including programs and tickets from historical events.

In a folder marked No. 9711, a brightly colored sheet reads, "Kennedy Johnson Inauguration 1961," with a picture of Kennedy and his vice president, Lyndon B. Johnson.

In folder No. 571 is a "Meet the Press" pamphlet bearing a typed transcript of an appearance by Kennedy.

The historical society previously received items that Landau had taken from its own collection, including a land grant signed by Abraham Lincoln to a former member of the Maryland militia who served in the War of 1812, which was valued at $100,000.

The thieves came twice to the Monument Street facility — first on June 15, 2011, and, again on July 9, 2011. It was during the second visit, in the reading room, that employees grew suspicious of the two men and called police.

"They were just acting suspiciously," Dockman Anderson said. "This little library was a crime scene."

The pair managed to steal items from Historical Society of Pennsylvania, the Connecticut Historical Society, the University of Vermont and the Franklin D. Roosevelt Presidential Library.

"Within 48 hours, what we thought was a local incident escalated into a multistate federal investigation involving the U.S. Attorney's office, the FBI, and the National Archives Security and Recovery Team," officials from the Maryland archives wrote in court documents.

More than 1,000 of the seized documents were later returned to Landau because he owned them legally, said his attorney, Andrew White.

White said Landau is "doing well and looking forward getting out."

The historical society has another reminder of the scandal: Video cameras now monitor visitors in the main reading room.