RCMP searched a home in Sackville, N.S., on Friday and found the Washington letter, which had been taken from Dalhousie University Library Archives, along with seized sheet music written by Henry H. Tillman taken from Memorial University of Newfoundland.
Officers also found books and war medals.
"This file just seems to keep on going," Cpl. Scott McCrae said Monday. "We're still looking for the dollar value of these items."
Police arrested a 23-year-old man, who is facing charges of obstruction of justice, perjury and possession of stolen property. The man's name has not yet been released.
Michael Mooseberger, head archivist at Dalhousie University, said that the Washington letter was written before the American Revolution.
In the letter, Washington dispatches a man named Moses Child on a mission to Nova Scotia.
Mooseberger said Washington memorabilia tends to be valuable.
"Washington material is very rare so I would imagine that it has significant value," he said.
$1M haul found in amateur museum
The case started in 2012 in Fall River, a community outside of Halifax, when police pulled over John Mark Tillman. He was charged with breaching the conditions of a house arrest, and an officer noticed a letter written by Gen. James Wolfe in 1758 in Tillman's car.
After investigating for several months, police tracked the letter to Dalhousie University and confirmed it was a stolen antiquity. They raided Tillman's home in January and found an amateur museum containing 1,300 allegedly stolen artifacts.
Mooseberger said he remembers Tillman as a lone researcher who paid a visit to the Dalhousie archives years ago.
"Usually they're inside jobs. They're usually somebody that was on staff that has systematically removed materials out of their holdings. But from somebody that was not on staff, from an individual researcher, this one certainly is up there as one of the most voluminous thefts across so many different institutions. It is pretty staggering," he said.
The thefts included rare editions of books such as Charles Darwin's On the Origin of Species, a full suit of armour, and a W.H. Yorke painting worth as much as $40,000.
Police said the goods were taken from several universities, museums and private collections and are worth around $1 million. They think Tillman built the collection up over two decades.
Tillman, 51, is charged with possessing stolen property, theft, obstructing justice and uttering forged documents. He is in custody and due back in court March 8. The police investigation into Tillman led them to the second arrest.
Police haven`t yet said how the Sackville is connected to Tillman. The Sackville man is due back in court April 24.
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