The Lonsdale boxing champion belt, awarded outright to Henry Cooper in 1961, sold for £49,250 at Bonhams' Sporting & Golfing Memorabilia sale in Chester, UK on May 29.
The gold heavyweight Lonsdale belt was awarded to the heavyweight outright following two successful defences of his British crown. He claimed the title in 1959, and followed it with defences later in the year and 1961.
It was the first of three Lonsdale belts Cooper would go on to claim, such was his dominance of the British heavyweight scene in the 1960s.
Lonsdale belts were first awarded by the 5th Earl of Lonsdale in 1909, who was a keen advocate of organised boxing matches.
This example featured an enamel portrait of Lord Lonsdale, several nine carat gold medallions, and engravings detailing championship fights dating back to 1937.
Dan Davies, a sports memorabilia specialist at Bonhams, commented: "Sir Henry Cooper was rightly seen as the people's champion and it makes me very happy to see the great interest in this exquisite belt.
"'Our "Enry' was a real gentleman, a hugely important characteristic in sport, which is sadly sometimes overlooked in these times where theatre and drama appear to take precedence."
The strong price is both a result of the public's great affection for the south Londoner, who died last year, and indicative of the upward progression of the boxing memorabilia market.
In November the trunks Muhammad Ali wore in his 1971 defeat to Joe Frazier made $173,102 at auction, a boxing memorabilia world record.
Ali's autograph rose in value by 13.38% pa between 2000 and 2011, according to the PFC40 Autograph Index.
We have a superb photograph of Ali with the Beatles, signed by the boxer, currently priced at £1,950 (approx. $3,050).