The crown/R here is not the repair proofmark, as the crown is shaped differently and the R is in Ornate script. It is more likely a mark of the original maker or craftsman. I'll try to find out.
BTW, in the original proof law text,the crown/G mark does not stand for Gezogen = rifled, but for Geschoss = bullet. Smootbore ball guns also bear this mark. So do smoothbores chambered for the 9.1x40R Tesching cartridge, as this case was used as a "garden" shot cartridge, but was also availble as a rifle load.