This is right from your page that I happened to stumble on while searching 1920 commercial Lugers void of proof marks "There is considerable variation in the 1923 Commercials. Proof marks may or may not be where they are expected, and all proof marks may or may not be present." AND 23 commercials are alphabet Lugers.....but I am not basing my opinion on this, is it from all the guns I have seen over the last 25 years. This is just one example, I also have a huge collection of Guns And Ammo books with Luger articles so you guys are going to have to give me time. But Ron agree's with me.
http://www.lugerforum.com/owner_gallery/owner1g.html
As I said, there might be Lugers with NO proof marks at all present and this is on your forum. I wish I could find more and I will get my guys name.