I just got off the phone with the production supervisor who worked the Chevrolet cycle bank in 1969 This guy is in his 80's and still sharp as a tack. He offered some helpful commentary on this topic.
Enjoy! I find asking these questions and the answers to be a refreshing dose of common sense.
"Don't over think this situation. The punch cards were cards created by key punchers in advance, that's true and there could be small errors here and there but in those days Fisher was a subcontractor to Chevrolet and as such Chevrolet was constantly looking to back charge Fisher for anything that did not pass muster at the 72 hour planning meeting. On the date issue the dates were not that fluid the usual date was part of Fisher's internal tracking system for the coach build so being incorrect as a part of doing business would cause havoc on both sides of the plant, so I just do not see that happening"
"When the Fisher coach arrived from Fisher Body at the Chevrolet cycle bank that is when we started calling it a body. The console operator at receipt inspection would first enter the production sequence number into the computer, while the console operator is entering the production sequence number and the body number off the body plate the computer then adjusted the RPO listing and parts needed for the build that was already entered in the mainframe at the conclusion of the 72 hour planning meeting when the build of the car was given the go-a-head. The arriving bodies were then simultaneously assigned and then stamped with the federally mandated Vehicle Identification Number “VIN” in Hidden areas on the body. The VIN information was then added to the build sequence number and the body number as an additional data field for the RPO content broadcast. There had to be computer agreement or the body would be rejected on the spot and Fisher would be on the carpet until resolved. You see major errors caught by Chevrolet would have the potential to cost Fisher big as a charge back so any build deviation was approved in advance at the 72 hour planning meeting, and was therefore part of regular production and not considered a deviation to General Motors".