Perhaps we could revisit the Cullinans in their various settings over the years. I confess this thread is to extend an O/T on the RCMB.
I contend that the crown of Queen Elizabeth the Queen Mother never had any Cullinans set in it. Further, the Cullinans were never connected with Queen Elizabeth (QM) being the property of Queen Mary and then of Queen Elizabeth II. At the 1953 coronation Queen Elizabeth (QM) wore her crown without arches, with the Koh-i-nûr on the front cross. The central diamond on the band was from a gift to Queen Victoria from the Sultan of Turkey and had occupied the same position on her Regal Circlet. Compare here the central diamonds on the bands. Queen Mary's is Cullinan IV.