There are a few manufacturers still in Stradella and there are a lot still in Castelfidardo. I was there last year and they're all over the town. Some are big names (Dino Baffetti, Paolo Soprani etc) but there are lots of small manufacturers too, many of whom don't seem to have a web presence.

I've got my father's 8 bass piano accordion (Foulestroop, I'd forgotten we'd discussed this before) I think it is just pre or post WW2. If I remember I'll try and get a couple of photos up for you to look at. The basses from memory are F, C, G and D and the major chord.