Vertigo,
This Luger definitely was a bargain at 320 Euros in my opinion.
The lack of proofs seems to indicate that it is a commercial pistol of DWM manufacture. The number marking on the sideplate "98" sideways is unlike any Luger numbering I have ever personally observed, but I don't have any printed references with me today... Perhaps someone else can comment on the numbering.
Since it is in the P-08 configuration complete with stock lug, it would have to have been manufactured after 1906 and before the DWM equipment was transferred (I think in 1933).
Please show us a closeup of the right side of the upper receiver where the proof and acceptance stamps normally are placed.
The finish looks original, and it has lived a dry but active life...
That's about all I can tell you off the top of my (bald) head...
Maybe someone else can recognize it.