Edited by Isabelle D on May 30, 2017, 8:33 am
I'm also inclined to think it's a detachable part of the larger brooch she wore as a hair ornament at King Carl Gustav's birthday last year.
Apart from the midnight tiara (als by Lynggaard) Mary never loans jewellery I believe. And that particular tiara is not for sale and can only be used by the crown princess. So I'm sure this brooch is her own possession.