The G33/40 was a small-ring Mauser based around the Czech vz.33.  It was primarily issued to German Gebirgsjäger (Mountain) troops.  They are very similar to the K98 but are a little shorter and lighter, and they have a full length handguard.

This particular rifle is a bolt mismatch 945 1940 G33/40.  "945" was the early war ordnance code for WaffenWerke Brün in Czechoslovakia.