Intriguing!! It looks as if there is a portrait under a diamond slice, similar to Queen Charlotte's ring with the portrait of George III, but I doubt if the Queen had a bracelet portrait done in this fashion.
In many paintings the Queen is depicted wearing a pair of pearl bracelets, most likely those given to her as a wedding gift. Each had 6 rows of pearls; one had a portrait of George III, the other a lock of his hair and cipher.
https://www.royalcollection.org.uk/collection/52211/ring-with-a-miniature-of-george-iii I suspect that the painting posted by ErikS displays an element of artistic licence and that West has, for what ever reason, depicted the central element with the portrait, as a large oval instead of round. In some other paintings the bracelets are depicted as having fewer rows of pearls which I think is also probably artistic licence.
Four rows of pearls with a round miniature portrait.
But, if Queen Charlotte had a larger miniature under a diamond slice it would be a significant find!
Edit. I noticed that in Zoffany's portrait the Queen's bracelet has an oval centre piece with the King's portrait, but the oval is not as elongated as in West's painting and of course the portrait is not covered by a slice of diamond or glass.
Previous Message
Does anyone know anything about Queen Charlotte's bracelet in this portrait?