What is the definition of "production"? According to Merriam-Webster the definition is
"2 a: the act or process of producing
b: the creation of utility
especially : the making of goods available for use"
We all know that S&W (with rare exceptions) did not keep records of when a gun was actually produced, only when guns were shipped. We also know that S&W did not ship in serial number order. Therefore, IMO, it is an exercise in futility to attempt to ascertain if a given gun is or is not a "first year production", because we flat don't know with any degree of certainty. If it was shipped during the first 365 days of manufacture, it would likely qualify. Other than that, all bets are off.
Case in point, I have a Model of 1955 that, according to Roy Jinks, was "manufactured in 1955" but was not assembled and shipped until March 1959. So, based on the definition of "production", it meets the criteria of a first year revolver. Based on shipping date, it obviously does not. An exercise in futility.
Roy also offered a good bit of wisdom:
"Charlie, collectors put too much importance in serial numbers and forget that these are manufactured products and that serial numbers to Smith & Wesson are only important for the legal requirements of the laws."
Often times, the same can be said for "birth year" guns. If it was shipped the same year as we were born, we call it a birth year gun. But if my gun was made in 1955 and not shipped until 1959, which year did I have to be born to call it a birth year gun?
It's all enough to make my head spin. To me, it makes little difference. But that is one of the things that makes our hobby so interesting and entertaining.