I can answer a few questions off the top of my head, and I am sure others will chime in.
"what is the little "pocket" for on the inside flap of the holster?" This held a loading tool for the magazine, if you load a box or two of ammo, your thumb gets pretty beat up.
DWM is the manufacturer
To figure out the barrel length, ensure the gun is empty, then stick a pencil down the bore, the length of the bore can be determined in that way.
serial number 73xxx Usually signifies a commerical made gun, someone told you it was a commerical, because I see you listed it here and in another area?
Has it been taken apart, all matching must include many different small parts also.
Take a look at Tech and General Info on your left, provided you came into
www.lugerforum.com and you can see a lot of information.
Are there other markings, such as proofs on the right or left side?
Can you scan it in or provide digital pictures?