Muhammad Ali remains the 20th century's greatest boxing icon, but Joe Frazier was among his most formidable opponents: one of only two men to ever beat Ali.

Ali was among Frazier's former friends, colleagues and adversaries who led tributes after the former Olympic and Undisputed World Heavyweight boxing champion lost a battle with liver cancer, aged 67, earlier this week.

Among Frazier's victories was his defeat of Ali on points in 1971's legendary "Fight of the Century", the duo's first fight at New York's Madison Square Garden.

As with many key events of the '60s and '70s, the fight became linked to wider social upheavals at the time - particularly the Vietnam War. Ali had publicly denounced the conflict - and was barred from fighting for three years for his dissent - while Frazier represented the conservative, pro-war movement.

Frazier's memorabilia, including this autographed photo (top) and signed is selling at Written Word Autographs later this week

Today, both Ali and Frazier remain icons whose lives, and conflicts, continue to captivate new generations of sports fans and collectors.

Ali's collectibility has proven itself over the past decade. The average value of his autograph has risen in value by 298% over the past 11 years. That means if you'd bought a Muhammad Ali signed photo for just £250 ($375) as recently as 2000, it could today be worth £995 ($1,500).

Elsewhere, the robe Ali wore into the ring before knocking out Chuck Wepner-March in 1975 made a mockery of its $8,000 estimate in 2005, selling for $30,000.

A pair of early training gloves, signed "Cassius Clay", sold for $22,000 just last year, $18,000 above estimate. And, back in 1997, the trunks Ali wore for The Rumble in the Jungle fight against Foreman made $50,000, $15,000 over their estimate.

More recently, Paul Fraser Collectibles had the pleasure of selling a pair of Ali's shorts to a lucky buyer.

Collectors are obviously doing their bit to preserve Ali's career and legacy. But what about Frazier's?

Muhammad Ali’s status as a 20th century icon means his ‘collectible legacy’ is firmly established in high-profile sales, like these Ali sweat trunks recently sold by Paul Fraser Collectibles (click here to find out more)

Following the legend's sad passing, the onus on collectors is now stronger than ever to ensure that his life and times are preserved.

You'll have a chance in two days when The Written Word Autographs of Tamworth, New Hampshire, auctions a pair of Frazier's boxing gloves. This Everlast leather boxing glove (left hand) is signed and will appear in the sale with a $125-200 estimate.

Other items in the sale include a Joe Frazier auctioned 8" x 10" promotional black and white photograph.

Both memorabilia pieces could now sell for considerably more as collectors move to commemorate the fighter's death - and ensure that Joe Frazier's memory lives on through his memorabilia.

The Written Word Autographs' sale takes place in two days' time on November 10. Online bidding will be available.