A sapphire and diamond ring. Photo Christie's Image Ltd 2014

Set with a cushion-shaped sapphire, weighing approximately 18.81 carats, flanked on either side with cushion-shaped diamonds, weighing approximately 2.37 and 2.31 carats, to the pavé-set diamond detail on the hoop, mounted in platinum, ring size 5¾. Estimate CHF160,000 – CHF220,000 ($183,584 - $252,427)

Accompanied by report no. 69839 dated 19 September 2013 from the SSEF Swiss Gemmological Institute stating that the sapphire is of Burmese origin, with no indications of heating

Report no.13080240 dated 27 August 2013 from the Gübelin GemLab stating that the sapphire is of Burmese origin, with no indications of heating, and an information sheet on unheated sapphires

Report no. 6157251020 dated 4 March 2013 from the GIA Gemological Institute of America stating that the 2.37 carat diamond is F colour, VS1 clarity

Report no. 2141486325 dated 30 July 2012 from the GIA Gemological Institute of America stating that the 2.31 carat diamond is F colour, VS2 clarity

Christie's. GENEVA MAGNIFICENT JEWELS. 14 May 2014, Geneva -http://www.christies.com/