I was at a family friends last night and he showed me a K98 mauser that he says his grandpa brought back from germany during the war. It looked like a regular mauser german marks ,but had a weird contraption to the left of the rear site. It is made of steel quite heavy and big,and has a level with a bubble in it. Also the trigger had a swiveling plate on the right side that said K98 on it in if you pull it rearward it will fire the gun. It had a regular front sight. He also had a P38 his grandpa brought back with holster and extra magazine. He also had his grandpa's M1.30 carbine. Awsome guns with history.

Sounds like it was set up for grenade launching.  The level would have been used to set the elevation.  Not actually seeing it, this is my best guess.

Does it look like an angle can be pre-set so that when the bubble indicates level, the rifle is at that angle (with the butt on the ground).  If so, then probably is set-up for grenade use.

Dave.

Yeah the device was shaped like a half moon and had something similar to a quick release bike tire latch in the middle. I figured it might be for grenades but it has nothing on the end of barrell, either way a cool rifle, not to different from my M48.