While I agree that styles would have influenced whether QEQM wore the collar in public, I personally feel it would not have suited HM. I think it might look stunning on the Duchess of Cambridge, although we have yet to see her wearing a collar, "dog collar" style necklace.
JohnAF, thank you for referring us to Ursula's site.
Ursula, I had not previously read this section of your site. Many thanks for the information.