I think that Margaret, Countess of Jersey may have been dressed for the Devonshire House ball of 1897 as seen in the photo below. The National Portrait Gallery, UK says that a photo from the same series was taken in 1897, but does not link it to that particular ball. The image I found was published in a magazine in 1901.



Detail


It seems that the same diamond chain necklace could be divided and was later worn in the fuller version by Patricia Richards, wife of the 9th Earl of Jersey, whom she married in 1932.

Patricia in 1932


Patricia also wore a portion of the chain as a head ornament in 1934.



The diamond riviere worn by Margaret, Countess of Jersey also appears to have been worn by Patricia for her presentation at Court as a married woman in July 1932.



Detail


The tiara worn by Patricia is the only one I have seen worn by a Countess of Jersey; however, the style suggests to me that it is a twentieth century jewel.

This was the only tiara I found Patricia wearing.
Below are some images of her at the Opening of Parliament in 1932.

1932


1932



The large diamond cross worn by Patricia to the Opening of Parliament in 1932 was also worn by Margaret, Countess of Jersey.

[Apologies. I'll post the images later. Just now Photobucket has decided its customers warrant the no delivery service, yet again!!


As Patricia Richards was an Australian, part of the honeymoon was spent in New South Wales where her father was a grazier near Cootamundra. Her husband's grandfather, the 7th Earl, had been Governor of New South Wales between 1891-1893.

In Sydney the young Earl and Countess attended a garden party at Government House. With her pearls the new Countess wore an interesting diamond brooch.



This marriage was relatively short lived. For those who are interested this obituary from the Sydney Morning Herald has more details on her life. https://www.smh.com.au/national/countess-of-jersey-from-nsw-country-girl-to-london-socialite-20170208-gu7w0y.html