There has been a lot of discussion about them online the past week because Boucheron have launched a new collection which includes similar pieces which draw inspiration from them.

The thing is a couple of posters have said they were bought by Elizabeth II's uncle the Duke of Kent at Cartier in 1937 (and the link below supports that), however no explanation has been given how they ended up as an 18th birthday gift from George VI to Elizabeth II in 1944 - the Duke having died in 1942, why would the Duke buy a gift for his niece on her father's behalf 7 years in advance?

https://www.xpeditionmagazine.com/post/x-luxury-queen-elizabeth-ii-wore-a-boucheron-aquamarine-and-diamond-double-clip-brooch

Any clues. I know Princess Marina had money troubles after her husband's death, any idea if these were maybe belonging to her and she sold them to her brother-in-law the King?