The other issue is that correctly interpreting proofmarks requires a bit more than just reading a book. For example, there's the issue of reproof, which can confuse things considerably. I've seen more than one case, on this BB, when I thought I had the proofmarks figured out and someone added something I'd missed. Or corrected something I misinterpreted. And that's with the Wirnsberger book plus all of Baron Engelhardt's and Lee Kennett's articles on proof readily available to me.
Here's what it all comes down to: this is a great place to ask technical questions like that, and to learn.
