The aquamarine clip brooches were a gift to Princess Elizabeth in 1944 for her 18th birthday from her parents, King George VI and Queen Elizabeth.
The brooches are art-deco in style, made with baguette diamonds and aquamarines, and were made by Boucheron, says the Royal Collection, but they were (mistakenly) identified as Cartier by Leslie Fields in her book, The Queen’s Jewels.
The clips can actually be worn as one piece, and it has been seen on Her Majesty this way in the past, but she usually places them as seen, in a diagonal setting. Occasionally though, they are set on top of one another.
Because of its clear and blue stones, The Queen of course tends to wear the pair with blue outfits, and occasionally white.
Notably, she has worn the piece to meet with the Obamas for a private birthday lunch in 2016, for a reception to celebrate the work of The Earl and Countess of Wessex in February 2015 and during her State Visit to Ireland in 2013.