A diamond ring. Photo: Bonhams

centering a cut-cornered rectangular-cut diamond, weighing 6.67 carats; enhanced by a circular-cut diamond 'X' motif basket and pavé-set diamond mount; signed Tiffany, Schlumberger; estimated total diamond weight: 2.20 carats; size 6 (partially obliterated signature). Estimate: US$ 200,000 - 400,000 (€150,000 - 300,000) (£130,000 - 250,000)

Accompanied by GIA report #2155618715, dated August 20, 2013, stating the diamond as: D color, VVS2 clarity.

Bonhams. Fine Jewelry. October 17th, 2013. New York.