HM Queen Astrid of Belgium née Her Royal Highness Princess Astrid of Sweden wearing the original version of the Nine Province Tiara. A flexible diamond bandeau in a stylized Greek key motif topped with 11 large diamonds on spikes.
Hoppé - Lady Nancy Astor (nee Langhorne), wife of Viscount William Waldorf Astor, wearing elaborate headpiece composed of crown (probably set with Sancy diamond which belonged to Queen Elizabeth I) and drape of fabric and pearls.
Kate's most famous piece of borrowed jewelry would have to be the Cartier "Halo" tiara that she wore for her wedding day in The tiara was purchased from Cartier in 1936 by King George VI (the Duke of York) as an anniversary present for
Chicago socialite Rose Movius Palmer wearing the Westminster Halo Tiara as altered, with the Arcot and George IV diamonds replaced with turquoises. (Replacing with turquoises is economical, but not very appealing.