After comparing it could actually by a Castell-Rüdenhausen tiara at all. A ntiawra which looks similar was once worn by the groom's gtrandmotehr Fürstin irene zu Castell-Rüdenhausen and by Duchess Donata of oldenbrug at the Wedding Ball of her son Pricne Georg friedrich of Prussia. But the pics from this 2 occasions are very small and not the entitre tiara is visible on them so it is hard to tell if is the same or not.