A square, 32.01-carat emerald-cut diamond ring that billionaire philanthropist Leonore Annenberg bought for her 90th birthday sold for $7.7 million at Christie's on Wednesday. About the size of a walnut, the flawless, colorless diamond is flanked by two pear-shaped diamonds. Annenberg died in March at the age of 91. She served as U.S. chief of protocol during President Ronald Reagan's first term – a position that carried the rank of ambassador. Her husband, Walter Annenberg, a billionaire publisher and ambassador to Britain under President Richard Nixon, died in 2002.