This brooch is part of the Wuerttemberg jewels, which is being auctioned by Sotherbys.
It was made in 1928, and belonged to Princess Eudoxia of Bulgaria. She gave it to one of her nephews in 1928. It's made of rose diamonds and emeralds, with gold details and a gold pin.
It ended up belonging to a Viennese family, the Wuerttembergs. It's a beautiful relic of a by-gone age.