Left side of frame. Just above the trigger guard. The format on mine is 3 letters and 4 numbers (for example - ABC1234)
No serial number = no answer.
Smith and Wesson is the make.
No serial number provided.
Not a valid S&W serial number.
1977
@1987.
@1983
1916
No serial number given.
Serial number.
Look on the butt of the revolver.
Made @ 1981.