Peter,
What is most puzzling about your gun is :
1. The refinisher (who did a nice job) seemed to have a chance to do a nice blue on the chamber and seemed to have work 'around' it altogether...I cannot, for the life of me, try to figure out why he/she would have skipped a reblue of the chamber...on your M2 pistol.
2. Wooden magazine has that tell-tale "ridge" of wood running through the bottom that is usually a Swiss '24 Bern magazine attribute...but someone seems to have tried to add "Navy" concentric rings (poorly though...).
BTW...here is a photo of a Luger that has been "freshened-up" along its bluing, but the area around the chamber engraving was left alone...as not to impart damage to the gold inlay...
On your gun, I am not sure what the refinisher was trying to retain...buy not doing the chamber...
Maybe a comment Vern made above makes sense...a die-hard Portuguese collector may want such a defaced gun...so maybe the restoration artist was "saving" the defacement area to prove it was one of the defaced guns...???...too bad he just did not leave the entire gun alone...
I woud also like to challenge the "defacement" topic a bit...
If the folks in power in Portugal felt so strongly about removing the traces of their loyality to their former King, why would not all of their service arms have been recalled and had all chamber crest removed. Maybe this was done "un-officially" in the field and by a few misanthropes, only...???...