404219 went out September 9, 1922-----don't have anything close on the other side.
Ralph Tremaine
And the answer to your question about date of manufacture is no----we very seldom learn of manufacturing dates---just shipping dates. The only relationship between the two can be guesstimated with reasonable accuracy depending on the particular model and type. In your case it is reasonable to assume your gun was shipped rather quickly after it was made simply because M&P's were fast movers----unless it's a target model, which tended to hang around for a spell. Special orders for any model and type likewise can be assumed to have been shipped more or less immediately upon completion----depending on what's special about it. Weird sights (fronts) are fairly common special orders---and they didn't make up a gun for those sights. They simply changed the sights on an in-stock item. The good news is all your guesses may be considered deadly accurate because (almost) nobody can prove you're wrong. I know the year (only) of manufacture of exactly one of my guns---and I learned it quite by chance. It's a rather obscure target model cursed by the fact there are likely more of them that won't letter than there are those which will. Needless to say, I wanted to be as certain as possible mine would letter before I turned loose of my money. I called all the experts, ending up with Jinks. He told me the gun shipped in 1941, said it was very likely a "legitimate" item (based upon the serial number----and the neighboring numbers)---and just casually mentioned it had been made in 1938. I suspect he knew that the same way he knew it was "very likely"----the neighboring numbers. And----there IS a God-----it lettered!!