Re: Use Serial number to determine Chiefs special age ?
No upper sideplate screw, so post 1955.
3" Heavy barrel introduced 1967.
Pinned barrel pre 1982.
Diamond grips, pre 1969.
Put them all together and I come up with 1967-1968 if the grips are original and 1967 to 1982 if not.
Did you pull the grips and see if they are numbered?