Rose Fitzgerald Kennedy, wife of the American Ambassador Joseph Kennedy, wears a diamond floral loop tiara borrowed from the Countess of Bessborough for a dinner at the French embassy in London, March 1939

Helena Montagu, Duchess of Manchester (born Helena Zimmerman; later Lady Kintore) wears the Manchester Tiara, made by Cartier in 1903, for the coronation of King George V of the United Kingdom in 1911; the tiara is now on permanent display at the Victoria and Albert Museum in London

Mary Victoria Curzon, Baroness Curzon of Kedleston, Vicereine of India (born Mary Leiter) wears a diamond and pearl tiara with a colored central gemstone in an official portrait, ca. 1901; read more about the jewels dispersed in her will over here!