According to the blog this cabochon emerald was a single jewel apart from the 7 emeralds used to make the brooch of the emerald parure.
I need to correct myself, the Prussian Tiara was given to Sofia as a wedding gift upon her marriage to Juan Carlos.
Frederika also acquired the huge Cartier Sapphire pendant from a Greek businessman, the pendant previously was in the possession of Queen Marie of Romania. It's whereabouts is unknown to this day.




https://royalwatcherblog.com/2022/08/30/queen-fredericas-emerald-pendant/