This jewel caught my eye and, thankfully, it has a royal connection. For the link to Catherine the Great please see the caption for the news item, which was published in 1935.
I hope that someone has additional information. Hopefully, this jewel is still with the descendants of Prince Felix Yussoupov and the Grand Duchess Irina but, I realise, it may have been sold at some stage. (I know there are many spellings of this family's name, so please excuse my choice if you have strong ideas about spelling. I am unsure of the correct version.)
I wonder if anyone has a modern colour photo of this jewel or even just the two black pearls, if the jewel was broken up.
There are few gems as seductive as a magnificent black pearl, particularly those with the peacock/green overtones, and so I would be most interested to read of, or see, the colours of these black pearls.