It is a diamond clip brooch, the top four leafs are identical to the bottom four leafs. Queen Sophia wore one part of the brooch in a photo by Gosta Florman.

The contrast in the photo is very bright, but you can spot it above Sophia's bracelet (later CP Martha's diamond bandeau/bracelet):



The contrast is better in this drawing:



Princess Christina of Sweden has worn it as two separate brooches several times.