Jared, welcome to the forum!
The 1918 has the stylizied DWM on the toggle which was the manufacturer.
Proofs? (see on your left under tech information if you came through
www.lugerforum.com) Tell us what and where proofs and markings are located.
There are forms in this section, where you can print out and then write down pertinent information.
Are there any letters next to or under the serial number?
That is my standard questions, but then I looked closer at your pictures, and they show that the toggle is a DWM, which was the manufacturer, that it is proofed on the right in the imperial manner (although I didn't look close at them).
It looks in nice shape and I love the Lange or more commonlly called "Artillery" Luger, as they were issued to artillery units, machine gunners, some NCO's, where ever they needed a pistol, but almost carbine like gun. Do some searches, look in the artillery section and you will find lots of good info here. There were wood holsters made for many of these and you can find them, but they are expensive. You can buy a period magazine for it and make it "more" original.
Ed