A 25.80 carats Type IIa diamond ring, by Harry Winston. Estimate CHF2,400,000 – CHF3,400,000 ($2,417,518 - $3,424,818). Photo Christie's Image Ltd 2015

Set with a cut-cornered rectangular-cut diamond, weighing approximately 25.80 carats, between tapering baguette-cut diamond shoulders, ring size 3½. Signed Winston for Harry Winston 

Accompanied by report no. 6173229537 dated 17 August 2015 from the GIA Gemological Institute of America stating that the diamond is D colour, VVS2 clarity; and a Diamond Type Classification letter stating that the diamond has been determined to be Type IIa. 

Christie's. GENEVA MAGNIFICENT JEWELS, 10 November 2015, Geneva