Or could it be the Art Deco ruby bracelet pictured in Angela Kelly's book Dressing the Queen (third bracelet from the bottom, page 85 of the book)? That would be coherent with the fact that Queen Elizabeth II was wearing the Barings ruby necklace and Queen Mary's ruby cluster earrings for the 1990 State opening of Parliament (picture posted by adca)
Here is another picture of the 1990 State opening of Parliament - unfortunately, the jewels are hardly visible: