I strongly suspect that the ruby necklace, which was stolen in New York (as per my first post) and was said to have a certificate from the French government attesting to its authenticity, was either one of the two necklaces sold in the great sale of French Crown jewels in 1887 or contained rubies from the parure. If so, then the rubies can be traced to the Duchess d'Angouleme, not her mother, Marie Antoinette.
But there are a lot of mysteries to solve.
The larger of the two necklaces from the French Crown jewels is known to have survived with only a slight modification (see V Meylan, Christie's page 166), and Vincent Meylan suggests that a ruby necklace which will be auctioned on 12 November 2019 in Geneva by Christie's might be a reworked version of the smaller necklace. That necklace came from the collection of Cornelia, Countess of Craven.
See Vincent Meylan at https://www.instagram.com/p/B4dbYceIvwB/
Also see the lot notes in the Christie's catalogue (lot 127) https://www.christies.com/lotfinder/jewelry/mid-19th-century-ruby-and-diamond-necklace-6229238-details.aspx?from=salesummery&intObjectID=6229238&sid=7417bfa1-03a2-4ecd-ad9d-11abaaabbf71
The necklace appears to be the same as the one worn by her mother, Mrs Bradley Martin (as a lower necklace) in 1897.
Apart from the necklace stolen in New York in 1935 and the jewels sold by Sir Godfrey Baring in 1928, I have seen another report of a ruby necklace said to contain stones originally owned by Marie Antoinette.
That necklace was said to have been worn by Mrs Claude Leigh, an American lady who featured extensively in the UK press from the late 1920s and during the 1930s.
Mrs Claude Leigh
The Leighs were wealthy and her jewels reported on extensively by the press. The earliest reference I have found so far to her ruby necklace is from early 1930, and reports continue throughout the 1930s, so I think it is unlikely the Leigh necklace was the one stolen in New York in 1935.
Perhaps the press references to Mrs Leigh's rubies having been owned by Marie Antoinette are hyperbole. But it is possible that her husband purchased the rubies sold by Sir Godfrey Baring. The million dollar question is -- is there any basis to the claim that the Baring rubies were once worn by Marie Antoinette? So many mysteries!