As for the choke marks being stamped in English, someone on another site mentioned this also. It seems odd someone would go through the trouble to do that if they didn't actually measure the bores and constriction and open them to those measurements, no? As you noted, looks like patterning necessary.
Would the 2 3/4" also been added later or would Germany mark both 2 3/4" and "/70" for the chamber length in mm?
You'll find, when you measure bore diameters and choke constrictions, that there's a great deal of variation from one maker to another. As for the 2 3/4", I'd guess that was added in Germany. Those Royals were imported by Stoeger (that might even be marked on the barrels as well). Therefore, the Germans were kind enough to give us Yanks something we could understand in terms of chamber length--especially back in the 50's and 60's, before we were paying much attention to the metric stuff. I had a Sauer 20ga from the 1930's, imported by Abercrombie & Fitch. That gun was also marked 2 3/4", right on the face of the extractor luggers. Once again, I expect that was done because it was made for export to the States.
