Don't be alarmed if you do see some pitting in the bore. It invariably happens. These master cylinders are open to the environment via a small hole in the side of the cap. Make sure that hole is open even though it will allow humid air in. The master cylinder won't function properly over time if that hole is clogged.
As far as inevitable pitting goes, most of the time it is not located where the cups ride in the bore which is all that matters.
