I wonder if there was more than one source, or a NOR LOS difference. Mike I can't answer that one Mike.
I would assume that the answer was no. Many large corporations tend to use one printing source and many of those are a wholly owned company of the parent corporation. When I worked for Ticketron a division of Control Data corp all our printed needs came from our own printing house that was run as a for profit company. Other vendors, competitors and theaters purchased ticket stock, will call envelopes, seating charts etc from them even if they were not on our ticketing system.
I Seem to remember a thread someplace about some printing house in the Detroit area that was a GM holding corp and at bankruptcy had been sold off but failed under new ownership and the contents and plates were being auctioned off. And think they also did decal sheets etc for model car kits, and the like. But I have never seen anything about GM having a printer division. Maybe someone from PR would let us know who printed stickers and vehicle documentation in the 60's