Be aware: you refer to a "P38 Luger". The P38 and the Luger (P08) were two very different pistols. What follows, though, should apply generally to both of them. Generally speaking, Nazi symbols were not usually found on German WW2 weapons. There were markings denoting the manufacturer, which could have been combinations of letters and numbers, there were some (e.g. Walther PP and PPK) which had what were essentially commercial markings, and there were stamps showing the weapons had been inspected by the "Waffenamt" (Weapons Office) before being accepted, --- some of these looked sort of like stylized Nazi Eagles. Finally, they might have had unit markings showing what organization owned them. But overt Nazi symbology (e.g. Swastikas or SS Runes) on the guns was pretty rare, and seems to have been mostly on presentation or personal arms, rather than issued ones. (The German Navy used a marking from 1934-45 which included a swastika under the nazi eagle with an M below that marking.) I don't doubt that in some cases symbols were filed off, but I suspect it was pretty rare. If you can provide a photo of the gun and the area which was "filed off", we might be able to give you more information.