The 599.10 carat Centenary Diamond was discovered on July 17, 1986. In its rough form it resembled an irregular matchbox. It took a select team of master cutters almost three years to complete its transformation into the 273.85 carat diamond it is today. The Centenary Diamond, which is now the world’s largest top color, flawless, modern cut diamond, was unveiled appropriately at the Tower of London in May 1991.