I have in my archive files an old picture of the tiara, and it is labelled as 'Kaiserin Augusta-Viktoria Pearl Tiara' (Augusta-Viktoria of Schleswig-Holstein was Kaiser William II's first wife):
But I admit I have not found any picture of the Empress (nor of any other previous Empress) wearing this tiara. I do not even remember from where the attribution to Kaiserin Augusta-Viktoria comes.