For others following who are perhaps new to the Cullinans, Queen Elizabeth II has worn The Cullinan III and IV Brooch, as it is now named in The Queen's Diamonds, a number of times since inheriting it from Queen Mary - who wore those two a lot !!
Cullinans ! and II
To the best of my recollection, only ! and II are now set in the regalia and, yes, they are removable.
I don't think the crown of Queen Elizabeth (QM) ever had a Cullinan set in it. The drop-shaped diamond set on the cross above the orb was the Labore, from Queen Victoria's necklace to which it has been returned with a crystal displayed in its place on the Queen Mother's crown. Its central diamond on the band was from the Regal Circlet and was among jewels given to Queen Victoria by the Sultan of Turkey.
But we detour here. The jewels discussion is more appropriate for the Royal Jewels of the World message board - until we get to another future thread planned for here on the RCMB.
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