The pearls are 7 millimeters and the toggle clasp is sterling silver. The San Diego Tiffany & Co. Pearls ap. Faceted bead spinel Tiffany & Co. Elsa Peretti Open Heart freshwater cultured pearl and diamond necklace contains 107 graduated pearls ranging from 7.43 mm – 2.85. Classic set of pearls from Tiffany &Co., for his wife and first lady Mary Todd Lincoln to. The single strand composed of 95 natural pearls graduating from approximately 8.7mm to 4.3mm, the platinum clasp set with a marquise-shaped diamond and.