Consider that the buck tag (depending on plant and year) was a way for the office to communicate to the workers/builders of the body. So the information needed to be converted to "line speak" (for lack of a better term) so that what came out of the body build section was what you wanted to come out. Sometimes that meant that grouping multiple options together on one code (GT and Mach I) for a certain operation (hole, bracket, body panel) reduced the number of codes, confusion and got the job done.
Does not mean that the specific car got all of the option just the body panel detail related to what every it was.
Not sure if I described that very well.
Line managers have told me that they changed the coding fairly often, when needed. One described a small pocket size decoders some of the workers carried. Stack of individual sheets of paper with a cardboard front and back "covers" held together with a single brad
