Princess Alexandra wears the pearl setting of the Ogilvy Tiara, April 1963 (Keystone/Getty Images)

If you’re only going to have one tiara in your royal jewelry collection, it had better be a versatile one! Such is the case with Princess Alexandra’s tiara, a convertible piece which can be worn with a number of different gemstones.

Alexandra wears the original hair ornaments, ca. 1956 (Pictorial Press Ltd/Alamy)

The tiara was made out of a series of pearl and diamond floral hair ornaments that Alexandra wore before her marriage. Above, she wears the ornaments in a portrait taken around 1956.

The sapphire setting of the new floral tiara (Everett Collection Inc/Alamy)

Around the time that she wed Angus Ogilvy, a son of the 12th Earl of Airlie, the floral elements were integrated into the design of this tiara, which also features diamond ribbons trailing around and between the diamond flowers.

Alexandra wears the turquoise setting of the necklace at the Midsummer Nights’s Dream Gala charity ball, in aid of the British Red Cross, June 2001 (Myung Jung Kim/PA Images/Alamy)

The piece also has a coordinating necklace, which was patterned after Queen Victoria’s Diamond Jubilee necklace, and various coordinating earrings. The parure was a gift from Angus, who had commissioned Collingwood to make the set for his new wife.

Alexandra wears the tiara as she, Angus, and Princess Marina depart for a ball on the night before their wedding, April 1963 (Keystone/Getty Images)

Alexandra wore the new tiara for the ball held at Windsor Castle on the night before her royal wedding in April 1963. While Alexandra has worn many tiaras during her lifetime — including her mother’s diamond fringe, the Kent Festoon, the Russian Pearl Bandeau, and the bandeau that became the Kent pearl fringe — this tiara is the only one that Alexandra personally owns.

Princess Alexandra (with Prince Philip, Queen Juliana, and Princess Margaret) wears the tiara during the state visit from Queen Juliana of the Netherlands, June 1972 (PA Images/Alamy)

It’s just as well, then, that the tiara is convertible. The pearls in the sparkler can be switched out for other stones, including sapphires and turquoises. The necklace is also convertible in the same way; its pearls too can be swapped for other gemstones. Different earrings with pearls, sapphires, and turquoises complete the extensive parure.

Alexandra wears the sapphire setting of the tiara at a Variety Clubs dinner reception, April 1972 (Everett Collection Inc/Alamy)

It’s been years since we’ve seen Alexandra in this tiara in public, but that’s largely a function of her advancing age and her reported physical discomfort wearing jewels like tiaras. (She’s still a very active member of the royal family as her health permits.) It’ll be interesting to see whether Alexandra’s daughter or daughter-in-law, who are both commoners, will ever have a chance to don the family diadem. Perhaps at the next British coronation?