The ZF-41 was a tiny 1.5x optic made in large numbers by Germany during WWII. It is a long eye relief design, mounting over the rear sight of a K98k, and allowing unimpeded up for stripper clips for reloading. These scopes are generally though to have been complete failures, and a huge disappointment to German snipers. Well, they were disappointing to snipers - but that is because they were never intended to be used by snipers. The ZF-41 was an early example of a designated marksman's optic - something to allow the best shot in a squad to get that little extra capability to make tricky shots. It was put into service with snipers because it was available in much greater numbers than proper 4x sniper scopes, and couple be easily added to a rifle in the field.
Karl and I took a reproduction ZF-41 and K98k, and put it through some timed tests to see just how useful or useless it really was - and we were very happily impressed at the results!