I do know J-F - I think it is the Vanguard.

The tell tales signs for me are the 3 leaves and the bow that is right at the very bottom of the brooch (almost awkwardly from a design perspective).

Also - and maybe I am reading too much into this - the Vanguard is a brooch given to Princess Elizabeth for launching the HMS Vanguard in 1944 (I think I got the date wrong in my previous post).

So I can see HM choosing this brooch for the review a series of naval vessels.