Thanks! I had not seen that before (ever) It looks like some of the 22 match single shots: Hammerli, ect.
The extra side knob looks like it allows the sight to be taken off? Is that the makers name on the side?
DRGM, Deutsches Reich Gebrauchsmuster (German Reich Registered Design) came up on google.
Looks like a hammer from a Colt SA, too.