I have read that Queen Mary gave her crown to George V for use by future queen consorts, so it is no longer private property.
--part of Previous Message-- : : One question. In your final list of circlets : available to the Queen, you list Queen : Mary's and Queen Elizabeth's circlets. By : these, do you mean the crowns without the : arches? Since they were consort crowns, and : the Queen uses the George IV diadem for : official occasions, she has never worn those : circlets, but I understand that they are : private property. Displayed, of course, : with the Crown Jewels in the Tower. :