Rottw. is the abbreviation for Rottweil (yes, where the dogs come from!).
The Pulverfabrik Rottweil-Hamburg AG, in Rottweil became part of RWS (Rheinisch-Westfälische Sprengstoff AG) which itself is now part of the RUAG-Ammotec group. So the cartridges were actually made in Germany for the Austrian rifles. Up to WWII the big German manufacturers made ammo for just about the whole world apart from the UK and USA.
Source: RUAG-Ammotec company history.
Patrick