So this stamp circled in red is a second (different) crown? I couldn't make it out, it kind of resembled an eagle or bird with a shield on its chest to me. Need to look at the pistol under some magnification, I guess. I didn't really see the "crown over crown over U" listed in too many of the online "identify your Luger's markings" sites out there (although I haven't searched too heavily here for that specific stamp yet).
The stamps on the right side of the receiver match up with #15 at this link:
http://www.lugerforum.com/lugermarkings/proof-2.html
So that would be correct for a 1914 DWM military pistol. Can anyone make out the "fraktur" letters on the receiver in my original post and tell me what they stand for? I found a chart but I'm having trouble reading them.
Serial number on the front of the frame (below the barrel) is 2031; there appears to be a "k" in script below that, although that looks like it has been partially stamped out by an "x" in block lettering. Would that serial number block correspond to a 1914 DWM? Serial number on the receiver is just 2031, but the font is noticeably larger, so I suspect it is force-matched. I tried several different shots to get the letter below the SN to come in clearly, but it's difficult to photograph as it's on a curved portion of the frame.
I also found another "eagle" type of stamp on the side of the breechbolt (2nd photo)