What is this thing?

[Ron Wood]

I think John is right on target that the recoil link was not properly in place. If you let the toggle down slowly, on most Lugers it will stop in an unlocked position. That is where the sear engages the firing pin and there is enough resistance to preclude the mainspring from fully closing the action. However, with this procedure, the toggle does not close as fully as shown in the first photos.

A point of information for first time Luger owners. It is best to store a Luger in an uncocked condition. If you lower the toggle as described letting it stop at this open point, then pull the trigger (ONLY ON AN EMPTY WEAPON!!!), the action will snap shut. That is one way to close the toggle without leaving the firing pin cocked. A better way is to slowly lower the toggle while holding the trigger fully to the rear(Once again, ONLY ON AN EMPTY WEAPON!!!), then the sear never engages the firing pin and it remains uncocked.