Almost all elaborately engraved guns were presented to someone important. I'm surprised you didn't know that! And they were picked up off a dead SS after a fierce hand-to-hand under the Brandenburg Gate and brought home in Grampa's duffle bag when he returned from Germany!
And strangely enough, elaborate firearms only seem to have been presented to someone of Hitler's inner circle! Look! It has Goering's initials on it! Anyone else with the same initials was undoubtedly executed immediately before the presentation ceremony.
An old friend once told me he was offered Japanese swords, rifles, helmets and militaria from a boat that pulled up alongside his ship around the end of WW2, and the people on board were doing a bang-up business. Oddly enough, all the items purchased were magically transformed into "battlefield pick-ups" between the time of purchase and home port. Just some more of the magic of firearms. Same with people coming back from Europe after WW2. If you had any idea how many "SS General's personal sidearms" have been bought and sold over the years, you would laugh. Or cry.
Without substantial documentation to back up the guns' stories, most are just stories.
I am feeling particularly sarcastic today, so please forgive me if I seem a bit vitriolic.