[Ron Wood]

Let me see if I can clear this up. The lip is the projection on the frame that catches the lock on the toggle. You noted that it has dished toggles. In the right toggle knob there should be a machined slot for the toggle lock assembly. The lock consists of three pieces, the locking latch, a spring and the pin that secures the latch to the toggle knob. Since the Luger in question has the frame catch, I suspect that the lock assembly has been lost from the toggle. These are replaceable and I believe Lugerdoc (Tom Heller) stated he has some.