I think that this video may help in identifying the brooch.
At 1.18 minutes Queen Mary can be seen releasing balloons as in the photo I posted above.
The view of HM's brooch at 1.26 minutes suggests to me that the brooch has a much smaller gemstone at the centre than what the photo I posted suggested.
--Previous Message-- : I wonder if anyone can identify the brooch : Queen Mary is wearing? : : Below is a poor screen shot. : : : It comes from the documentary The Royals : who rescued the Monarchy part 2 at circa : 43.42 minutes. : : : :