On June 3, 1997—just three months before her tragic death—Princess Diana dazzled in a sky-blue beaded gown and splendid necklace of diamonds and South Seas pearls at the British National Ballet’s Swan Lake. “There were more pictures of her wearing this necklace than any other jewelry she ever wore,” says Arlan Ettinger, president of Guernsey’s auction house in New York City. After the gala opening, she returned the necklace to the British Crown Jeweler, Garrard, which was busy making matching diamond and pearl drop earrings. “This was Princess Diana, not just a normal off-the-street client,” says Ettinger. “Every stone had to match precisely.” The necklace and earrings—known as the Swan Lake Suite—were ready when news broke of Princess Diana’s passing. With the blessing of her grief-stricken family, the set was discreetly sold to a British lord whose wife had a passion for jewels. “But she had been girlhood friends with Diana and she couldn’t imagine comfortably wearing them,” says Ettinger. So they went to Guernsey’s, which auctioned the suite—the only substantial jewels ever worn by Diana to be sold—to a Texas furniture magnate for a high six-figure price tag. They’ve since been sold again, to a new owner overseas.