During the Belle Époque, women decorated the bodices of their dresses with devant-de-corsage brooches, and this version by Cartier is a masterpiece of the form. Diamond ­magnate Solomon Barnato Joel commissioned the piece with three stones—a 34.08 ct. pear shape, a 23.55 ct. oval shape, and a 6.51 marquise shape—from his own South African mines, and Cartier master ­craftsman Henri Picq added lily-of-the-valley links and pavé-set palms when he completed the piece in 1912. Little wonder the brooch sold at Christie’s Geneva for $17.9 million. “Our buyers are collectors, investors, and