Here is the bobbin case after Nick Ciancio did his thing:
I now have an extremely rare old machine that has a free arm and uses common 15x1 needles! Allowing a 15x1 needle to punch the metal out is a bad idea. Just Google for the result and you'll find pictures of destroyed cases.
I'm more than happy to recommend Nick to anyone in Melbourne who has a vintage machine. He's very friendly, can repair anything and really loves the old machines.
Oh and I should mention that in a comment on my last post I said that I was a little disappointed in the 320s stitch quality. Checked the needle height and it was a mm or two out, which had also put the timing out. Spent 20 minutes fixing it and she sews much better now.