5. Lee Harvey Oswald archive
This archive relates to Oswald's life in the run-up to the assassination of John F Kennedy in 1963, the first assassination of a US president since William McKinley in 1901.
We know now that Oswald acted alone, but conspiracies continue to dog the plot to this day. This archive, which sold at Heritage Auctions for $50,000 in 2008, features a wealth of letters and other materials that detail his life up until that day.
In one letter he writes to his brother Robert: "I want you to understand what I say now, I do not say lightly, or unknowingly, since I have been in the military as you know, I know what war is like.
"1. In the event of war I would kill any american who put on a uniform in defence of the american government - any American -.
"2. That in my own mind I have no attachment's of any kind in the U.S.
"3. That I want to, and I shall, live a normal happy and peaceful life here in the Soviet Union for the rest of my life."
4. Samuel Bland Arnold's confession
Samuel Bland Arnold was one of the conspirators in the assassination of Abraham Lincoln in New York in 1865.
Bland was pardoned in 1869
In his confession he relates his meetings with the assassin John Wilkes Booth.
Throughout he claims to have had no knowledge of the plot to kill Lincoln, and instead recounts a plan to kidnap the president and turn him over to the confederacy.
He writes of Booth's mania, which led to an altercation between the two men in the bar: "After arguing to great length...it culminated in a very exciting and violent controversy between Booth and myself..
".where Booth in his rashness and madness, finding he could not swerve me from my purpose...threatened to shoot me or words to that effect..."
He was sentenced to life in prison that same year, but was pardoned in 1869 by president Andrew Johnson.
3. Gunpowder plot skin book
In 2006, a book allegedly made from the skin of Father Henry Garnet, a Jesuit priest executed for his involvement in the gunpowder plot, sold for ?�5,400 at Wilkinson's Auctioneers in Doncaster, UK.
Garnet's crime was to have been made aware of the plot, through hearing a confessional by chief conspirator Robert Catesby, and to remain quiet as he hadn't wanted to break canonical law.
This led to his being hung, drawn and quartered (and possibly turned into a book).
2. Operation Valkyrie manuscript
The July 20 Plot was an attempt to dismantle the Nazi high command through assassinating Adolf Hitler and setting a contingency plan known as Operation Valkyrie in motion.
Valkyrie would pass control of the state to the regular German army, allowing the conspirators to seize control. Claus von Stauffenberg, a Wermacht officer, was the mastermind behind the plan.
As it played out, Hitler was not badly wounded and the plotters were rounded up and shot.
An account of the bombing, narrated by SS officer Adolf Heusinger, came up for auction at Nate D Sanders in 2012 but failed to sell.
1. Nixon Watergate letter
The Watergate scandal was the defining political scandal of the 1970s.
A break in at the Democratic National Committee HQ at the Watergate complex in 1972 was linked back to the president and members of his cabinet.
Nixon was forced to fire his advisors, among them John Ehrlrichman. On June 12, 1973, Nixon wrote him this letter: "I'm sure you know how much I miss Bob and you.
"No President ever had two more able & loyal advisers. I feel for you both in this difficult time. And I feel for your families...I only wish I could help. Keep the faith--!...All will come out OK because we are right."
Unfortunately for Nixon things didn't work out that well for him. He resigned in disgrace the following year - the only president in history to do so.
The letter made $52,500 at Christie's New York in December last year.