Tranished safety - CZ 75b SS

[5-SHOTS]

I'm 99% sure that the brown color on CZ's Stainless internals is caused by somekind of heat treatment. My father's CZ 75 Stainless with brushed finish exibits the brown color also on the internals, expecially the slide stop. Where it was brushed the brown color is gone. It doesn't look like a coating to me, it looks more like it is part of the metal surface that changed its colour after the heat treatment.