I used the following serial # breaks to easily estimate when a K frame I am interested in was made.
k 100,000 1950
k 250,000 1955
k 400,000 1960
These are general guidelines rounded to even numbers but they work well to tell me what to expect in the way of grips, model/dash #'s, 5/4/3 screw guns.
This doesn't cover all frames, in all era's and all dash #'s, but this is where my interest lies, so works for me.