Here's a royal couple we've never seen (and won't see together again -- they're divorced now!): Prince Amedeo, Duke of Aosta and his new wife, Princess Claude of France. Amedeo, who now uses the title Duke of Savoy, is the son of Princess Helene of Greece. (Claude and Amedeo's son, Aimone, would later also marry a Greek princess, Olga.) He's also a great-grandson of King Amadeo I of Spain and a great-great-grandson of King Victor Emmanuel II of Italy. Claude, who married Amedeo in the summer of 1964, is a sister of the Count of Paris, the current Orléanist claimant to the French throne.
The sparkler Claude sported for this ball isn't a French piece, though: it's the Aosta Knots and Stars Tiara. Claude also wore this diamond tiara on her wedding day, and Amedeo's second wife has worn it since his divorce from Claude. (You can see a picture of this tiara on display at an exhibition here -- scroll down.) Not my favorite tiara -- diamond stars and all that -- but it's certainly an impressive piece!