It states that here the Queen wears a "fringe necklace had been set with family diamonds for Q. Adelaide and adapted for Queen Victoria to wear as a diadem".
This could well be the piece that is now referred to commonly as the Hanoverian or George III fringe.
The royal collection also refer to it here, in relation to The First of May painting, as they say:
"Queen Victoria wears a diadem of a sunray design said to have been made by Rundell’s for Queen Adelaide".
"On the Queen's head is a diamond diadem of sunday form, said to have been set by Rundell's for Queen Queen Adelaide using family diamonds."
Although now, what these actually refer to, whether or not they are one and the same pieces, or actually two separate pieces. And what has happened to both the piece and the stones now, is yet another question and mystery to be solved.
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