I'd better explain. It might not be a perfect match.
From my reading of Field she says that 'head ornament' of the Queen's (worn in Canada in 1970) was used in 1971 to add to the aquamarine tiara the Queen had made in 1957.
However, we now think we have seen Sophie wearing that head ornament in 2012.
I'm now thinking, if Field is right, then other gems have been added to the carcase and that head ornament is now worn by Sophie. Not a match after all.
Or Field identified the wrong 'head ornament' and the 1970 one was never dismantled.
--Previous Message-- : I'm very sorry Nellie, but from your two posts : I actually do not comprehend your : alternative theory about what the tiara as : worn by Sophie might consist of...?