Ring containing Louis XVI and Marie Antoinette's hair which was given to Madame de Tourzel, the Governess of the royal children. Apologies for not remembering where I found this image. Please advise if you are the owner and I will include the credit. I believe this ring is in the Musee Carnavalet, Paris.
Jewelry of Marie Antoinette
The Princesse de Lamballe as a Child
Empress Sissi of Austria with her stars in her hair (detail)