Lovely find of the silver one!
There may be in silver but pot ones less likely as they would have been thrown (out of fashion etc) or discarded as useless as only one left etc. or broken. Look how many single pot plate are found and difficult to match.
Also, in pressed glass of that period which was very early, right at the beginning, it might (I stress the word might) have been easier to simply make a round or oval mold?