Pistols with all correct numbers, but..

[LugerVern]

All matching can be a good indication a gun is all original but it can also be miss leading.

With just a little study you can tell a DWM font from a Mauser or Simson or HK part, so the mixing of manufacture parts isn't a real problem. For example an Imperial DWM "3" will usually have a rounded top and one from Mauser a flat one. The sear bar on a DWM will be SN stamped on the upper step and one from Mauser on the lower step.

Finding a correct part both in manufacture, SN and time is a difficult thing to do. The odds are against you, yes is does happen but with very low frequency. In cases where you suspect a parts gun of original parts you then need to look at the overall condition of the individual parts. If a trigger retains 90% straw and the other straw parts only 40%, you can be pretty sure someone got lucky and found that rare part they needed.
It doesn't happen very often at least not to me

Vern

[alvin]

Originally Posted by LugerVern

It doesn't happen very often at least not to me

I believe it's less common on 95% (and up) blued guns, but more common on lower blued guns. On higher guns, that "skin cancer" is the main concern, on lower guns, ....., originally I thought lower ones are less troublesome, but found that's not neccessarily to be true, the "organ" could be an issue. Each range has each range's headache. There are also guns with mixed "symptoms".