Calibrate Leica FOFER rangefinder

I have a FOFER rangefinder I use with my model Ia. When set to infinity, the image does not align with distant objects; I assume it's out of alignment at other distances as well. Is there a way I can re-calibrate this myself? Would most Leica repair technicians be able to calibrate this?

You need a peg spanner (or improvise one) to loosen the ring in the middle of the dial that surrounds the screw then adjust the rangefinder with the screw, finish by tightening the ring with the spanner. Be sure that when you set infinity it really is a long, long way away.