I do think it is the diamond ring from the Diamond Chandelier Drop Demi-Parure (from King Fahd of Saudi Arabia - 1987 state visit).
Same design with the earrings from the demi-parure (floral style).
Queen Elizabeth II wore the ring during a state visit in Germany in 1992).
Please find below photos from the net (what kate wore and other sites) :
[img] upload image[/img]
[img] herbergement image[/img]
The Duchess of Cambridge has been spotted with what looks like a massive marquis cut diamond ring on her right ring finger. Nice to see her wear some more bling.
Beth it's very good to hear you say this space will definitely continue and HM's outing of a necklace you had assumed was another one in her mother's collection does give credence to the many statements about your work and abilities as matters of fact, so please accept what we the posters are saying about you with grace for they are true.