To the best of my knowedge there are no such things.
As I understand it, Linley is the outright owner of the hoop diamond necklace, to do with as he wishes. And I assume some items worn by Lady Sarah are her private property also, to do with as she wishes also.
--Previous Message-- : OK, perhaps Royal Collection was the wrong : identity. Probably more correct would be : something along the line of "Windsor : Family Collection" or "Queen Mary : inheritance Collection" :