Maybe it is a collection watch of high value (I admit I have absolutely no knowledge about watches), but it is indeed "only" a watch.
Camilla usually wears another more simple watch, with a black leather strap:
(Photos respectively by Sang Tan/WPA Pool/Getty Images and by Chris Jackson/Getty Images)
So the one worn on your picture had maybe something special, in connection with the event attended by the Duchess of Cornwall (maybe an aviator's watch?).
--Previous Message-- : Thank you for these photos Arthur -- which : show that this is a watch. It is the last : thing I would have thought about as it is on : the Duchess' right arm. I was thinking too : conventionally! : : I still suspect that the bracelet part may : have diamonds, but perhaps I am imagining : things in my thoughts about glitter!