I don't believe your pistol started life as an L P08, Erfurt did not produce the long pistol except in 1914 with 1914 dates. The proof and inspection on the right chamber are from Erfurt.
Erfurt followed the directive to produce all receivers with the LP08 sight clearance cut from 1916,
DWM did not- the presence of the cut on a DWM receiver would indicate birth as an LP08.
I don't see the serial number on the left side of the chamber- but it just may not be in the pictures.
Erfurt did produce spares, this could be a spare Erfurt barrel, but I would expect to see an Erfurt style proof eagle on the barrel- are there other markings not in the pictures?
The British proofs may obscure some other markings, and the barrel itself is somewhat rough near the receiver flange. The Crown N proof on the right of the barrel in the second picture is also an anomaly.
Pictures of all markings will help add to the story, as would a picture of markings in the inside "well" of the frame where the takedown lever passes through. A picture of the milling in the rear of the frame area also will tell the story of DWM vs Erfurt.
More pictures !
