That's always a good question, and on an individual piece pretty hard to ever really know.

First and foremost S&W is (was) a factory, they made guns which were working tools. I don't believe they ever imagined their everyday standard products would be analyzed, categorized, and fussed over the way we do today.

I think it was common well, more common than we think, that an order had to get out so they simply fit whatever they had to finish the piece, complete the order and ship it.

/c