It would be great to see the Greville emerald tiara (if it still exists) resurface again - not only for its own interest and craftmanship, of course, but also because the British jewel collection is actually quite short on emerald tiaras. The only emerald tiara I have identified in the British collection is the Vladimir Tiara, in the version with the Cambridge emeralds (which are even only substitutes for the original pearls).
Meanwhile, there are quite a lot of emerald necklaces in the British collection (I consider only the main line of the family):
1) the Delhi Durbar Necklace (made by Garrards for Queen Mary in 1911):
2) the Cambridge emerald choker (also made for Queen Mary, presented by Queen Elizabeth II to Diana, Princess of Wales, and never seen again since Diana's death):
3) the Greville necklace:
4) the Godman necklace (presented to the Queen in 1965 by the daughters of the late Frederick DuCann Godman):
5) The Emirati Emerald Demi-Parure (a gift from the President of the United Arab Emirates during the Queen's Gulf Tour in 1979, or during the Emirati State visit to the UK in 1989, if I well remember; the set includes a necklace, a pair of earrings, a bracelet, and possibly a ring):
6) A modern emerald and gold (?) demi-parure, of unknown origin, comprising a necklace, a pair of earrings and a bracelet (Queen Elizabeth II has worn this set only twice, in 2000 and 2002, for two film premieres):
7) Diana, Princess of Wales' Emerald Demi-Parure: the late Princess of Wales was seen at least once with an emerald necklace which is none of the necklaces mentioned above:
8) Camilla, Duchess of Cornwall's emerald demi-parure: Camilla has worn a few times a large necklace of rectangular emeralds, with a matching bracelet and a pair of matching earrings, which are supposed to be a Saudi gift:
Have I missed one necklace?
So, with at least 8 emerald necklaces in the main line of a family, it would be fine to have at least one or two extra emerald tiaras!