A diamond and ruby 'Ibex' brooch, Jean Schlumberger, Tiffany & Co. Photo courtesy Bonhams.

the head pavé-set with round brilliant-cut diamonds, accented by a marquise-shaped ruby eye, extending scrolling fluted antlers; signed Tiffany for Tiffany & Co., Schlumberger; estimated total diamond weight: 1.20 carats; mounted in eighteen karat gold and platinum; diameter: 1 3/4in. Estimate: US$ 4,000 - 6,000 (€3,000 - 4,400) (£2,500 - 3,800)

Bonhams. Fine Jewelry. October 17th, 2013. New York. www.bonhams.com