Right you are, and since Bill's Lugers, the 1938 and the 1941 have their toggle link in the white I think that indicates that Lugers at Mauser were first blued then assembled, which why the toggle link is in the white.
As you said few know how to dissamble the toggle link of the luger that is why they dip it without dissamble it first, or because it is done by mass production as have been done by Russian armouries with captured Lugers.
Alf