Whilst we all know exactly how passionate Queen Mary was about Jewels, l'd be surprised if she felt she *MUST* have Xenia's Emeralds, simply because they are so [very] similar to her own families 'Cambridge Emeralds'.

Why bother when she had 'Shedloads' [a British term] of Cabochon Emerald Drop stones already ?

If she did buy them perhaps it was to help out her [suddenly] 'financially embarrassed relative?

If the 'mystery' Necklace is Margaret Greville's, then that's different, since the recipient of her legacy, had no significant Emeralds of her own.

'Off topic' l know, but it occurred to me that i've never seen a photo of Queen Mary wearing ANY Ruby jewellery, and the only piece we know she bequeathed to Princess Elizabeth was the 'Rose of York' Bracelet [which she received as a wedding present], rather than acquiring herself.

It seems she had no affection for Rubies ?