I've seen a few nickeled DW's over the years and almost bought one, a 15-2 with custom sights.. From the pics, it looks like it's been done very well, and if I was to guess, and that's all it is, a guess, it's a factory job. The aftermarket plated guns I've seen were all done where you could tell it was aftermarket due to detail lost when the bluing was removed and the gun polished up. The hammer could be plated, or it could be from a 715 and be SS. They did odd stuff like that once in a while. There was a new 15-2 in a Vegas gun store in 1982, with a stainless hammer and trigger. Nothing noted anywhere about it, that's just how it came. I almost pulled the trigger on it, I really liked the look of it.