Originally Posted by Unk
As to galling as I recall was a very early issue in SS semi-auto pistols. The reason given was that the same exact SS could gall. The early fix was to use dissimilar SS and the problem was solved. Since that was many, many years ago would guess that new SS have developed and one non-galling SS is used.
THIS is correct.
Smith & Wesson found out the hard way in the 1980's with the advent of the second gen. 639's/659's that slides/frames of the identical SS material was an issue.
I still have a jar of Rigs STAINLESS +P Lube that was popular back then to avoid issues, before they figured it out.