The first thing I would advise is to not store the Luger in the holster as that can cause it to rust. I would take the pistol to a gunsmith to have him break it down and clean it properly. Luger disassembly/re-asessembly is not for the novice.
The markings DWM = Deutsche Waffen- und Munitionsfabriken (Geramn weapon and munitions works).
The name & on the holster, Franz Cobau Berlin 1935, is the manufacturer of the hoslter. They also made other miltary equipment. I am only guessing that the 1935 is the date the holdter was made.
Luger pistols came in a couple of differnt calibers (7.65 also known as .30 cal Liger and .9mm parabellum) and that should be stamped somewhere on the frame or barrel. Germans were fanatics about numbering everything, so check the pistol closely as all of the parts should have the same matching serial number (This includes magazines and holsters).
For the proof marks, take a look at this link:
www.collectorsfirearms.com/book-proof-marks.jpgThat little tool found in the holster is a combo magazine loading tool and screwdriver.
I am no expert on Lugers, but I would guess that this is a later model as the "Buttons" on the bottom of the magazine are metal and not wood like the earlier versions. Also, I believe that the toggle "Buttons" are flat and not scalloped or dished like the earlier ones were.
As for the value, that depends on many factors: condition of the pistol, matching serial numbers, when it was made and by who, and also any markings on the gun. Guns America had them listed from $750 to several thousand dollars. There are many Luger collectors out there that could give you more info on this gun if they had the serial number and more pics.