Hi,
The best way to establish if and how often a luger was fired, is to take a look at the toggle contact area at the frame (visible in your last photo). The blue will start to wear off pretty quickly, even after moderate use. I started documenting the wear patters on my reworked S/42 when I got it. After some 5000 shots it shows considerably less wear than the pistol in the bottom picture, so I guess the pistol was used and used well
Holster wear, on the other hand (muzzle and side plate island) develops pretty rapidly. Wear to the side plate was visible after only holstering it a couple of times.
War time pistols without wear to the muzzle area (left side) and side plate don't make me nervous, though. They are, 99% sure, refinished.