does anyone know if Hermes ever produced a silver whistle pendant?
In the Japanese catalogues, there are a few dog whistles. Is that what you're looking for?
if you can manage to get ur hands on one the japanese cataloges have a wealth of images that might be able to help you find the pendant you are looking for
I am not sure if this is what you are looking for, but rere's a photo of an H dog whistle on yahoo japan.