Hi,
All the Schimel pistols I have seen are pre-fixed GP (22) meaning they were gas powered, although there is evidence that an air powered variant was planned to be pre-fixed AP (22). I am not aware of any actual examples of this variant and can't really see how the design could be adapted efficiently to use air power.
You are right to be careful not to put any unnecessary strain on the cocking lever or delicate curly trigger as these two components aren't too robust.
Lovely pistols though which always go off with a satisfying crack adding to the enjoyment of shooting them.
I believe I paid £300 for this nice boxed and fully functional example a few years ago.
Regards
Brian