There is some information about it on Royal Magazin, where it is mentioned that it was a wedding gift from The ladies of Hampshire and the Isle of Wight. It was made of diamonds and rubies.
For me it seems to be some sort of buckle (?) bracelet, which apparently was quite popular around that time. There is one example in the Danish collection as well, made out of diamonds and rubies, with a band of gold. There is a picture of it in Bjarne Steen Jensenís book. If I recall correctly it belonged to Queen Louise (born princess of Sweden) and are part of the jewels she left to be passed from monarch to monarch.