A 19th century natural pearl and diamond brooch. Estimate CHF800,000 – CHF1,000,000 ($816,500 - $1,020,625). Photo Christie's Image Ltd 2015

Designed as a triple loop bow with double ribbon, set throughout with old-cut diamonds and suspending two detachable drop-shaped natural pearls, measuring approximately 12.3-16.5 x 22.5 and 13.9-16.0 x 23.5 mm respectively, circa 1870, 8.5 cm

Accompanied by report no. 81185 dated 14 July 2015 from the SSEF Swiss Gemmological Institute stating that the two pearls are natural saltwater pearls, and an Appendix letter stating that '... To find a matching pair of natural pearls of this size and quality is rare. The (...) pearls thus represent an exceptional treasure of nature'. 

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