There was an old post about someone finding one of these a few years back. It's a particularly scarce post-WWII Austrian issue border guard/customs guard Steyr M95. The 54 is the date marking for 1954. The ZW is the unit marking on the buttplate and stands for Zoll Wacht I belive (Customs Guard). Nice find! Let me know if you ever decide to get rid of it at some point in the future. They are very difficult to find! Can you post pictures of it?