Dan, no problem. If you look at the frame near the rear of the barrel and almost to the cylinder you should see a rounded pin end, (if the barrel is pinned). The process of pinning the barrel to the frame was stopped around 1982, so if pinned, your gun dates pre 1982, if not pinned it was after 1982. The serial number places it about 1981, so it should be pinned. The problem with S&W's is that nothing is absolute and the above information is based on approximations.
pwp, if I am reading your serial number correctly, J128XX, your gun should be of 1969 vintage and not have damond stocks.