Mistake or not, it's a very nice and popular hand gun. I have a K22 shipped in 1950 with that flat finish. It doesn't bother me much, but next to the 1973 M15-3, it's downright ugly. But I never really checked into why, as it seems their finishing processes seemed to have changed so many times through the years. I just chalked it up to manufacturing changes, whether for cost-cutting, environmental-friendly, or whatever reasons. I have a very nice low shot-count model 57, 6", that is as beautiful as it is a great caliber for playing with at the range. No fingerprints on that matte blue finish on those that came that way.