Need help with proof marks

[roy]

I have a 1918 DWM with both No 1&2 mags numbered to the SN of the gun.
There is a very,very,very small stamp just ahead of the rear site, it looks like a small circle with lot of short lines from the 11:00 o-clock psn to the one o-clock psn [looks like a drawing of some ones hair standing up after they stuck their fingure in a lite socket], at the 2,3,4,o-clock psn are lines that are longer, at the 6 psn is a captial D, at the 7 is another long line and nothing else back to the 11:00 psn.
Can anyone tell what it is?
FYI this gun was taken off a dead German Bomber pilot that had crashed in 1944 and was brought back in 1945. It has never been out of the owners hand until he sold it to me. It has never been in a gunsmiths hand.

The barrel was changed at some point in time. The proof marks on it are PTV on top of the bird with raised wings. Also when you look at the top of the barrel, just a little left of ctr. there is a bird with lowered wings standing on a globe and to the left of it is a much smaller bird standing on a globe with wings lowered.

On the front of the frame is the SN. number and just under it is a letter b. On the suffix chart #1 it is the center b. of the three shown.

Can any one can tell me what these marks mean, where all the gun has been, was the barrel changed when it came back from WW1 to be recondition, and how could it have ended up with a bomber pilot in 1944?

Thank you for your time and help.

You can e-mail at machgun4@aol.com