very nice gun - and it was not reblued when it was privatized in 1956. If it would had been reblued in this time, it would be black inside as well.
But you have the wrong magazine- that's a magazine for a Swiss DWM made pistol (1900 or 1900/06). The W+F magazines have no metal inlays. It should not be to difficult to find one and they are normally a little bit cheaper (at least in Switzerland)...
Alexander