Hi,
I dont know very much about Single Action systems, but normally in a Double Action revolver, this safety lever holds the upper position to the firing pin as long as you hold the trigger. By releasing the trigger, the lever will go down to safe position again.
I will keep an eye out for the manual of the german blank fire version, maybe there is a sparepart list with a picture in it... If I find one, I will post it right here.