very possible you will find marks of the ejector, firing pin and the action in general which lead you to the luger pistol. the barrel profil you find on the bullets may also be different from post war pistols.
the 7,65mm parabellum cartridge is rare in the rest of the world but on this point near switzerland and italy its a more common thing. in switzerland they like it because of tradition and in italy it was for decades a replacement for the 9mm Parrabellum civilians were not allow to have as a forbidden military caliber.
I have to admit that such cases are interesting. in the early 1990s there was a murder in germany when someone was shot with an old french army pistol M 35 in 7,65 long.
the case was made by 32 s&w brass the rim turned down and cut a new extractor groove, trimmed and loaded with 7,65mm Parabellum FMJ bullets.