The third link which Dave gave shows a depiction of a tiara design by Cartier. It is one of two designs Cartier did. I suspect that the tiara was never made as I have never seen photos of the Duchess of Windsor wearing anything like either of the two design.

I had seen the images of the Duchess showing both of the proposed jewels but, until I saw the Cartier Exhibition in Canberra in 2018, I never appreciated that these were proposals.

The sign at the Cartier Exhibition tells the story -- that photos taken by Dorthy Wilding in 1935 were enhanced with renditions of both proposals of 1937 designs.



The two proposals

1.


2.