Two examples in this thread of "open" guns that were apparently factory engraved. Seems likely that record keeping mistakes were easily made when guns were sent to the engraving shop.

As to the pre/post war serial situation, we know how crazy things were during the war and the transition to commercial production immediately following. I think that a number of guns or numbered frames set in inventory from the 1930s and were not assembled or shipped until after the war. Not really a mystery.

With so many different models sharing the same frames incorrect model number stampings are also easy to understand.

That unusual serial location on the old M&P is a puzzler. Maybe the serial was inadvertently left off and when the mistake was caught for some reason it was easier or faster to stamp it in front? Just guessing, here.

One could start a collection of S&W oddities.

__________________
No life story has happy end.