Lot 380. Impressive diamond and 59.88 carats, SI1 Clarity, treated fancy vivid yellow diamond brooch. Estimate 580,000 — 865,000 CHF (530,071 - 790,537 EUR). Photo Sotheby's

Set with a treated step-cut fancy vivid yellow diamond weighing 59.88 carats, further highlighted with step-cut and pear-shaped diamonds.

Accompanied by GIA report no. 5171525330, stating that the diamond is Fancy Vivid Yellow, Treated Colour, SI1 Clarity. 

It is understood that the brooch has been commissioned by the present owner from Harry Winston in the 1970s.