A great overview, thank you The Royal Watcher!

I know that the necklace was worn as a tiara by Princess Irene, although I don't think that it has been seen in recent years.

It is possible that Queen Frederika sold the ruby during her years of exile to raise funds. We know that the large sapphire was sold.

The rubies given to Queen Sophia by her mother have always intrigued me. As far as I know there are no photos of the tiara/necklace; nor, as far as I know, are there any rubies in the Greek collection which are unaccounted for. Did Queen Sophia sell them during one of the early periods of exile? Were they broken up and used in other pieces of jewellery? A mystery!