Patriot, I'm guessing that what you're seeing is actually 13/1. That's the original bore diameter, which in the case of that gun is .719 rather than the standard 12ga .729. (One good reason to own a bore and choke gauge is in order to measure the bores on such a gun, to see how close they are to their original diameter.) Quite a few German guns were underbored. My Lindner Daly is a 13/1 gun, and nearly 100 years after it was made, the bores still measure almost dead on at .719. That's a pretty strong indication that they have been honed very little to clean up problems (like pits)--if at all.
