Hi Peter,
In my opinion (and it is only that...), two things are working against your Luger...
1. Removal of the Portuguese chamber crest.
2. Loss of its original DWM factory-finish.
Either one would "kill" my interest in the M2...
Similarly if a Swiss Luger had its Swiss chamber marking removed but had the rest of its factory finish intact...I would still walk past the gun.
Yours has 2 strikes against it...in terms of being "collectible".
I would look upon such a gun as a "shooter"...for either condition but certain for both occuring on the same gun.
I have not heard of chamber crests being removed, routinely...can you share more info. on this..did the Portuguese do this after one King fell out of favor...???...
Here is the M2 on my gun :