One point to consider is that documentation followed the body on the line prior to the SPID or VIN being attached. After all, there is paint underneath the SPID label and the vin tags are unpainted.The last part of it, R47 is the 2-door, or 47 body style. I just thought of something about that other number. It COULD be...speculation only here...it COULD be the job sequence line number. Which has absolutely nothing to do with the VIN. It was primarily used by Fisher Body to identify the body structure parts to the car and ensure that body order was tracked before the VIN was affixed to the car. It used to be called a broadcast number or something of that sort. In the old days, the Fisher number was assigned and placed on the body tag and on the paper IBM card that sometimes was placed in the car, but later on, the tags (if applicable) didn't have the numbers on them, like in the late 80s. Perhaps it has something to do with that. But not all SPIDs had them. I think they only did that in the Pontiac plant. But not positive.
Again, pure speculation. Someone knows. It's got to line up with SOMETHING. They didn't put rando numbers on SPIDs.
Yet someone knew whether to paint the car a certain color or bother finishing the welds for a non-landau roof, whether to have studs and holes on the doors for snake blinder trim things done before the vin and SPID were attached.
Someone had to be able to confirm they were attaching the proper vin and SPID to a car, and, that sequence number on the label is the only thing that would realistically serve that purpose.