[ QUOTE ]
Something to remember with broach-marks is that the broaching machines used had a time line with respect to wear. In other words, not all original broach-marks look the same. The scratches grow more distinct as the broachers wear out. Dont judge one set of broach-marks against another as they both could be original. Just make sure those lines are straight!...........Bill S
[/ QUOTE ]
Very good observation. This is akin to forensic comparisons of bullets to a particular barrel of a particular weapon. The reason that you can match a single bullet to a single gun is that the machining process of making one barrel after another, degrades the mandrel or the cutting instrument used to make the barrel. So barrel #1 will have a different microscopic machine mark pattern than barrel #2 and so on.
The same can be said for the machines that were used to cut the flat surfaces on engine blocks. So if someone (like Jerry) has been identifying and recording particular patterns over a sequence of time from a specific engine plant, they can then render an expert opinion as to the originality of an ID pad surface.
Jerry, have you ever been called as an expert witness?