December 8 will mark the 70th anniversary of John Lennon's murder at the hands of Mark Chapman - and on the eve of that anniversary, a copy of Lennon's final album signed for Chapman by the ex-Beatle will be auctioned in New York, estimated at $850,000.

Whether this sale is merely of another piece of Lennon's legacy that ought to be preserved by collectors, or whether it crosses the line into morbidity, is open to debate. Needless to say, fascination with the killers of important historical figures is nothing new on the collectors' markets...

The anniversary of another famous assassination was also marked this week, on November 22: that of President John F Kennedy, who was shot with a sniper bullet while riding through the streets of Dallas with his wife, Jackie, in 1969.

You may not be shocked to hear that memorabilia of the man understood to have murdered JFK, the former US Marine Lee Harvey Oswald, has previously appeared at auction - although the tenuous links to Oswald and the values they command may come as a surprise...

The 1962 Dallas Taxi Cab, allegedly ridden by Lee Harvey Oswald

Take for instance the 1962 Checker Marathon Dallas Taxi Cab which is "believed to have been" hailed by Lee Harvey Oswald following his assassination of President John F Kennedy. The cab spurred lively bidding at RM Auctions in June, rolling past its pre-sale estimate to $35,750.

Who would spend $35,750 on a cab only "believed to have been" ridden by Oswald? The answer is the Historic Auto Attractions museum in Rockford, Illinois, where the taxi now joins a large collection of other Kennedy memorabilia.

What's more, collectors' fascination with the assassination of JFK doesn't only extend to his killer, but also his killer's killer. Two days after his arrest for President Kennedy's murder, Oswald was killed by Jack Leon Rubenstein - aka Jack Ruby.

To this day, mystery surrounds Ruby's motives for killing Oswald, with many historians suggesting that Ruby was at the centre of a mafia or police plot. When the fedora hat worn by Ruby as he shot Oswald auctioned earlier this year, this intrigue undoubtedly helped push bids to a final $54,000.

The $54,000 fedora worn by Oswald's killer, Jack Ruby

And it isn't only mysteries surrounding Kennedy's death which have led to big sales at auction. Intrigue surrounding the President's often complicated love life have also stirred the interest of bidders.

Take for instance a collection of letters written by Kennedy to his lover, a married woman named Inga Arvad, which appeared at Christie's in 2007. The secret letters, written in the early 1940s, give some very candid insights into Kennedy's personality.

The letters themselves are filled with sexual longing for Kennedy's "Inga Binga", his sense of humour and other personal revelations, such as his bitterness about the waste of war. Offering unprecedented insight into 'the man behind the mystery', Kennedy's love letters sold for $144,000- well above their $20,000-30,000 estimate.

And then there's his most famous (alleged) affair of all with Marilyn Monroe. Today, it is generally held that Monroe called the White House frequently, was possibly in love with him, and that married Kennedy eventually broke off the affair.

John F Kennedy's love letters to Inga Arvard, later sold at auction

Naturally, when possible proof of Kennedy and Monroe's affair emerged on the collectors' markets, bidders clamoured for a chance to own it and pushed the item's final value to $120,000.

The piece in question was gold Rolex watch believed to have been sent by Marilyn Monroe to JFK, inscribed "Jack, with love as always from Marilyn May 29th 1962." Kennedy reportedly told a White House aide to "get rid of it."

Little did Kennedy realise that ongoing fascination with his life, more than 40 years after his death, has made such items difficult to get rid of - and increasingly valuable on the private collectors' markets.

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