Belle Epoque Platinum, Gold, Natural Button Pearl and Diamond Circle Bow Brooch. Photo courtesy Doyle New York.

The circle brooch composed of and suspending 10 golden pearls approximately 6.6 to 4.4 mm., spaced by old European-cut diamonds, centering one old European-cut diamond approximately .40 ct., topped by a diamond-set bow, totaling 41 old European-cut diamonds approximately 1.35 cts., circa 1905. Estimate $3,000-4,000 

With GIA report no. 2155567363 stating that the button pearls are natural, saltwater, no indications of treatment. 

Doyle New York. Important Jewelry. Wednesday, September 25, 2013 at 10am - http://www.doylenewyork.com