Seems to me that they had a cutter on their mill that went south and damaged a couple of slides (likely quite a few more) and they made it all the way thru plating, assembly and function check. It happens, and it isn't as infrequent as one might think. The only thing about this scenario that surprises me, is how many of you are surprised it could happen… It would seem that QA and QC at S&W is for all intense and purposes nonexistent, and has been for several years now. In what I believe to be an effort to crank out as much product as possible, they have apparently defaulted to using the customer at the primary QC for their products which results in QA feedback from the CS department to implement preventative measures on the production line. Cost savings gone amok in my opinion.
Also don't forget the human factors here… We aren't talking about the highly skilled craftsman and artists of long ago hand fitting individual pieces together, but a much younger generation of CNC operators tasked with cranking out as much volume as possible. You think there is no way for a machine operator to miss a single defective cutter on CNC gang mill that is whacking out perhaps as many as a dozen slides at a time? Or that the person running them thru the plating tanks dozens at a time is going to catch it? Or even the person throwing in the striker, springs and what not… heck, they are likely doing a hundred or more a day! I can totally see this kind of quality escapement happening and am not the least bit surprised. And that is based off the assumption (and hope) that it was an escapement and got missed.. there is always the possibility that it DIDN'T get missed, but simply got thrown together because someone didn't care or wasn't worried about it…
In regards to the apparent wear that so many are concerned about, I don't see that either. The plating on my Shield is some pretty soft stuff, and I had far more wear than the OP on my pistol before I ever fired a single round, just from racking the slide with dummy rounds, disassembly and reassembly, and then a bunch of dry fire drills.
In short, I would be willing to bet that things are exactly as they seem (aren't they usually?) and that this is a brand new, factory test fired pistol that left the factory with a defect that was never detected prior to shipment. Not a big conspiracy… just a big QC escapement.