I too have such a prewar Sempert & Krieghoff Waffenfabrik Suhl "Semper" .22 lfb insert barrel, serial number 9197. But, other than your's, mine has the sliding adjustment points just like the postwar ones.

I guess your Einstecklauf is an earlier version, intended to be adjusted by filing or shimming the contact points. Or are there adjustment screws beneath those contact points?