Belle Epoque Platinum, Gold, Diamond and Natural Pearl Brooch. Photo Doyle

The three diamond-set looped ribbons centering 3 pearls, joined by swags of diamond-set leaves, suspending one drop-shaped taupe pearl approximately 12.8 x 10.6 mm., accented by 2 diamond briolettes, circa 1905, briolettes added later. Drop pearl: light gray, the front is cleanish with some iridescence, some rippling, the reverse has a lighter patch of gray with light taupe hue with faint hairline crack, does not break surface, roundish back, not flat, good luster. Button pearls: off-white with rose hue, slightly creamy & creamy which has faint hairline crack, medium to low luster.  
Diamonds: I-J-SI, one chip on facet. Good condition. 1 3/4 x 2 1/4". 
Sold for $22,500

With GIA report no. 2155019172 stating that the pearl is natural, saltwater, no indications of treatment.

Doyle New York. Wednesday, October 17, 2012. www.doylenewyork.com