The one on the left is the one I imagine you are refering to. It is an old ceramic mold, in fact I have it. I believe the original casting of the mold from this company was early 80’s.
I’d have to dig out my ceramic molds and find it to be sure, but I do know that while there is a resemblance, it wasn’t an attempt to copy Windstone as far as I know.
Kyrin