Hey, it's Frogpatch! Good to see you!!
Cool piece! It's clear you've done your research on this. As I was reading through your post I kept thinking "Germany," because here in the "Missouri Rhineland" it was quite typical for the 19th century German immigrants to put "feet" on cabinetry such as this, although usually the feet are much flatter. When you mentioned Pennsylvania the German connection clicked again.
I have not seen anything like this before, but have no reason to disbelieve you. It's a nice cupboard with some individual folk flair. I'd guess it to be about 1890-1910 and made by a craftsman of German descent, perhaps in a small town or in the countryside. Just my .02.