Buchsemann,
The einstecklaufs were installed in the right barrel to take advantage of the set trigger. You can buy one for the left barrel, but it has to be specially made. This is because the "convergence" built into them is opposite each other.
Ger,
The term "Klappvisier" would be "folding sight" in English. These were not automatic and were folded "up" by hand. One can be made easily enough from a common 2 leaf rear sight, by milling the standing leaf off. If you don't mind losing the automatic function of the rear sight, the simplest solution is to remove, label, and store the small rod in the barrel rib, that pushes it "up".
Still, the einstecklauf is a handy thing to have. I enjoy all of mine, although the one for my O/U combo is hardly used, so I can use shot.
Mike
