Princess Laurentien was also wearing a diamond brooch on her back to fasten ther order and golden earrings with (i think) moonstones and little diamonds.
I think i have not seen the pendant before. It is indeed very interesting.
There is a good photo of Princess Laurentien (and the pendant) on the site The court jeweller.

https://www.thecourtjeweller.com/2021/09/prinsjesdag-sparkle-in-the-netherlands.html