Many thanks for all the infos.
I didn't know the pearl was flat at the back.
I always love the stunning grand devant de corsage brooch Empress Eugenie had made with the pearls from the Crown Jewels Collection.
Curious to know if some other elements of the devant de corsage brooch have survived (I think of the two lower parts with wings and scallop-like shapes that would have made beautiful brooches on their own).
Thanks again Beth !