The pearl-festooned headpiece was passed to Queen Elizabeth II, before Princess Diana started taking it out for the occasional spin. Max Mumby/Indigo // Getty ImagesThe Diamond DiademPrint Collector // Getty ImagesAccording to the Royal Collection Trust, this diadem was made for George IV to use at his coronation in 1820. It was a favorite of Queen Elizabeth II (she liked to switch things up and wear it with pearls, emeralds, or just diamonds). The Five Aquamarine TiaraThe origin story of this tiara is a little murky, but we know Queen Elizabeth wore it to Canada in 1970. David Cairns // Getty ImagesThe tiara seems to have been passed to the Countess of Wessex, who has worn in on at least two occasions!