I guess their QC depends on maybe the day of week or a different assembly team or something like that. I just picked up a 637 this week and, cosmetically, it's the cleanest S&W I have never handled. Even under the grips, there isn't a ding or scratch or mark anyplace. Mechanically, it carries up strong on all five chambers, has a .04 BC gap, and locks up tight all the way around. Equally important to me – and I understand probably not important to normal people – the crane/yoke does not flex out with light pressure on the right side of the cylinder. The only small cosmetic flaw I can find is a couple of light scratches on one side of the hammer.
Truth be told, I got it from a kitchen-table dealer who had five or six of them NIB. The first one I checked was equally good cosmetically, but it had yoke flex and kinda loose lock up. I bought the second one I checked because it was near perfect as mentioned above. I liked the M637 so much that I did the same checkout on his stack of M442's. I selected the second one that I examined – but it will be April before I can afford to pick it up ...
But, there is another issue to mention. He has a 3-in 686+ he received recently. Mechanically, it is perfect with even a smaller yoke/frame gap than any of the J-frames. But, it has a noticeable flaw on the left side at the barrel/frame junction. Some steel was pushed up when the barrel was crush-fit onto the frame. It's too much to polish out and basically ruins the appearance of the revolver in my opinion.