Coro Duette?

This is my favourite dress clip set. I found it last year and had to have it. It's very pretty and in great condition. It has a patent on the clips for the sprung mechanism 1852188, which relates to a 1932 Elisha A Phinney design registration.

I've seen these sets online on where the brooch can be worn separately, but this was the first and so far only one I've been able to find for sale. I'd love to know for sure if it is definitely Coro. I've searched extensively online to no joy.