Needs some more info on this luger if possible

[intrepid3]

Hello, all I just recently picked up a 1917 DWM luger. I have found this forum to be quit helpful with identifying this luger even before joining. But it did lead me to more questions that I can't seem to find answers for, yet. So I figured I’d join and see if the folks here could help.

All the numbers match on this luger including the grips
A couple of my local gun shops told me that they would say that the luger is around 80-85% grading.

The 6th pic (proof-2.jpg) I barrowed/stole from this website. Line 15 shows the proof marks for this luger. Which according to the info that i found on this website say that this luger is a German military receiver proof. Found on DWM Lugers 1914-1918. Some one told me that each mark and its position has it own meaning as well as all marks together having a meaning. Is this true or not?

The 4th pic (Barrelmark.jpg) shows a rough drawing (sizing is not correct, best i could do with windows paint) of a mark on the barrel right in front of the proof marks, the top of (what appears to be) the Iron cross is pointed towards the rear of the gun, and the lower case m with long center leg points towards the front of the barrel. Can any one tell me about this mark; I haven't been able to find anything.

The 5th pic (Underrearsight.jpg) shows the markings under the rear sight when it is lifted. Can anyone tell me about these.

Thank you and hope to here some good feedback.