Recessed panel lines for a tool made in 1970 is impressive. I doubt they added them latter, because that change is not 'tool safe' as they say. It requires adding material to a tool, not removing it. Recessed panel lines are difficult to machine using traditional methods, and have only recently become economical with the introduction of EMD cutting technology in tool making that happened in the 80s.
Recessed panel lines for a tool made in 1970 is impressive. I doubt they added them latter, because that change is not 'tool safe' as they say. It requires adding material to a tool, not removing it. Recessed panel lines are difficult to machine using traditional methods, and have only recently become economical with the introduction of EMD cutting technology in tool making that happened in the 80s.