About the best one can do is grab hints here and there from the Stevens book and fellow collectors. And there are contradictions.
Some folks try to interpolate a rough date by dividing total production during that period by the number of years, but I believe production of commercial guns was rather nonlinear at times.
Contract-numbered guns, acquisitions and improvements in machinery, etc,. skew the numbers somewhat.
My one data point to offer is an FN with a S/N about 28600 that was made in 1950, based on it being a transitional model between several engineering changes. The question then becomes, is it numbered within the normal sequence or is it a contract number?
There was a thread a while back with some discussion on alll this. I'll see if I can find it.