Needs some more info on this luger if possible

[intrepid3]

Ok, I got some better pictures done today. Also I took the gun to a firearms collectors show this weekend and spoke to several of the military firearms collectors there. They all said that the gun had not been reblued or refinished. They also said that all parts appeared to be original; without completely disassembling the gun to be 100% sure. They also said that the gun was defiantly WW1 and could not see a WW2 remarking on it. I ask if they knew what the mark on the barrel was and on one knew.

Now to the pictures, in my original post i posted a picture (the 4th picture) that I drew up using windows paint of a mark I could not identify; after buying a better magnifying glass and getting a better picture my drawing was incorrect.

Picture 5 is the mark in the red square that I am trying to figure out. Does anyone know what this mark is and means?