man who knows... As mentioned by one prior poster, if its legit, I would guess a 1911 that was imported one way or another to Germany prior to hostilities. Think of the nice nickel Colt in Letters from Iwo Jima.
Maybe the stampings were part of the importation process or perhaps the gun was contributed to the war effort. Or even knowing how Germans love to document and stamp as many things as possible, perhaps some eccentric German officer insisted on carrying it in combat and had to have inspected and stamped.
The Germans even assigned an official number for captured 1911s: German forces also used captured M1911A1 pistols, using the designation "Pistole 660(a)
The double stamp Nazi Eagle is the biggest question mark though, never seen that before and it looks just too Hollywood. I wouldn't be surprised if the Waffenamts are original and some jackass decided to "Nazi it up" and added that Eagle, did it poorly and double struck it.