After a bit of googling, they match earrings displayed in 2016 Paris' Biennale des Antiquaires belonging to the late Princess Maria Francesca of Savoy, who married a Prince of Bourbon-Parma:

"a pair of earrings of Art Déco style, with large baroque pearl drops weighing circa 100 grains each. According to what I heard from M. du Daffoy himself, these earrings come from Queen Elena of Italy, born Princess of Montenegro (1873-1952), wife of King Victor-Emmanuel III of Italy. They were at some point given by Queen Elena to her youngest daughter, Princess Maria-Francesca of Savoy (1914-2001), who married Prince Louis of Bourbon-Parma (1899-1967)."

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