The -4 engineering change was in effect from 77-81. Call S&W and they will tell you when it left the factory.
@1961
Need a sn to date it.
@1992
You will have to call S&W
1976
1976-1977
1979
By the serial number. It is located on the butt of the weapon.
Call S&W and they will tell you.
Call S&W and they will tell you.
1950
If you call S&W, they will tell you when it was shipped from the factory.