I am looking at a 1917 DWM Navy proofed Luger.It is a mismatched numbered pistol " The stock lug was partially ground off.. A reproduction stock and holster
The questions
1. Can the Stock lug be rebuilt?
2. If it can be rebuilt would adding the stock change its classification to SBR (or something else). My FFL seems to think so and isnt going to transfer it if I purchase it.
3. Whats is the value of it? I am taking it on trade. From the pics it looks like most of the orig finish is worn. The bore is dark but no pitts. And it is mismatched numbers. Grips seem to be repro The trade im taking it on is $1800-$2000
Any help would be wonderful

That's a whole lotta money for a boogered up P08.  I personally would not do it.

+1

I wouldn't give more than $800 for that. I consider that shooter grade, not a collectable gun

The ATF exempted Lugers from the NFA.  Stock is good to go.  ATF Exemption