Reposting this in the HAQ forum as my public forum thread is just getting troll comments. Hopefully the WIS here can shed some light on this subject for me.
A number of modern watches seem to be incorporating nickel-phosphorous components, especially in the escapement. Rolex for instance uses a nickel-phosphorous balance wheel and anchor for their new 3255 Calibre:
Primarily this material is touted as providing magnetic resistance, but it also seems to be used in some high-end quartz watches like the recent Citizen Caliber 0100:
So what's the deal with nickel-phosphorous? Nickel is a ferromagnetic material, so how can this be insensitive to magnetic interference? And why is it being used for HAQ movements like Citizen's, where the timekeeping elements are immune to magnetism anyway? Does it provide other desirable qualities, like wear resistance or temperature stability?