I join Janet in her response. It is fascinating the Duke of Polignac! Thank you for introducing me to a tiara I have never seen previously.

Do you know if the jewels in the Museum were purchased, or were they claimed by the government at some stage?

I agree with Janet, the current configuration seems less than ideal, even though the tiara is mounted on a base which would raise it above all but the most voluminous of hairstyles.