Spectacular brooch! I wouldn't call it a prototype but perhaps a variation, and there are many. It's frustrating to come very close to a verified ID but it's not an exact match. I'm working on a Coro ID right now that's similar to your situation. The patent picture is almost identical, but mine has an extra piece. When you're pretty sure of the maker but can't confirm it, you can always "attribute" it to the maker, pointing out the similarities and letting the buyer decide for themselves. Either way, that brooch will sell itself on looks alone.
I'm not a hoarder! There's a price tag on everything!
