Excellent. Looking at the Fenton, Dugan and Imperial pieces I have to hand at the moment, I can see a distinct mould seam line central to the raised rim of the collar base, (which I presume is the snap line?) whereas as you say the Brockwitz is roughly ground - I had seen the grinding and just put it down as rather a lot of wear, but looking it with your knowledge, I can now clearly see that it has been ground but not polished.
Thanks again,