The best anyone can do is an educated guess. S&W did not keep manufacturing records, they kept records of when a certain serial number shipped from the factory. They did not ship in numerical order nor did they build in numerical order. A handgun was built, placed in storage along with others and when an order came in, the first one grabbed was the one shipped.
The only way to get an accurate ship date is to buy a letter from the historical society. Everything else is merely a guess.
Kevin