The answer is:
The Golden Jubilee
The Golden Jubilee is the largest faceted diamond in the world, weighing 545.67 carats. The stone was designed by Gabi Tolkowsky, who also designed the 273.85-carat Centenary Diamond, which is the largest D-Flawless diamond in the world. The Golden Jubilee was presented to the King of Thailand in 1997 for his Golden Jubilee - the 50th anniversary of his coronation. Prior to this event, the stone was simply known as the Unnamed Brown.