The Crown Jewellery
Excluding the Crown Jewels (ie the jewels in the Tower) there are just two categories: Jewels left to (or given to) the Crown by Queen Victoria, Queen Mary and King George V; and the rest, which are private property.
source: Suzy Menkes, "The Royal Jewels", Third edition 1988, Appendix A 'The Crown Jewellery'.
Menkes has given her sources as Twining Papers, Goldsmith's Hall Library; and The Royal Library, Windsor.
...................................................................The Crown Jewellery
Jewels left to the Crown by Queen Victoria:
The Diamond Diadem of George IV
Brilliant Regal Tiara (made in 1855 to hold the Koh-i-noor; diamonds remounted for Queen Elizabeth the Queen Mother's Crown; the four detachable anthemions from the Regal Indian tiara later forming what is now the Countess of Wessex wedding tiara)
Regal Indian Tiara
The Timur Ruby
The Diamond Collet Necklace
Two Diamond Collet Necklace
Diamond Fringe Necklace (stones from George III)
Duchess of Kent Amethysts
three Bow Brooches
Queen Victoria's Sapphire Brooch
Presents from the Prince Consort. These items were all left to Edward VII by Queen Victoria in her will, to be considered "as belonging to the Crown and to be worn by all future Queens in right of it", being bracelets, brooches, pins, and a Scottish pebble set as a brooch.
A collection of jewelled cockades, girdles, swords, orders, rings, bracelets, brooches, earrings, opals, pearls, mementoes, minatures etc etc.
Queen Mary gave to the Crown:
3 Indian armlets (1912)
Indian diamond, pearl, emerald and ruby necklace (1926)
Ring sent to Tower by Queen Mary 1919 and added to the Regalia:
Sapphire ring with ruby cross and diamonds given to Queen Victoria by her mother the Duchess of Kent in 1838
King George V gave to the Crown:
Snap of the Indian necklace (see above) made of a ruby ring given to Queen Victoria by a Maharajah.
Based on this list, and assuming it is largely accurate, the vast bulk of the Windsor jewel collection is private property, and strictly "hands off!".
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