Ed Poole provided some additional info to me via email:
When I was asked to look at the Mad Max one sheets, I pulled all the hi res images that I had available, which was 15-20. EVERY image I had on file was one or the other. The logo was tiny so I asked the dealer to send me a close up photo of just the logo. It very clearly stated GCIU on the logo.
ALL of the posters that I had with the union logo had that SPECIFIC union logo.. the GCIU logo. The GCIU did not come into existance until 1983 making it impossible to have been printed before that time.
That is NOT to say that there are not any other posters out there. It was common during this time to have studio issues. If any exist, I did not have them on file. I am only comparing these 2 specific posters and identifying the R83.
Now to answer your question on the possibility of being a Canadian issue. - it has nothing to do with it.
You have to understand the Canadian distribution. There were 4 Canadian NSS branches. They were regular warehousing branches just like most of the other US branches. 3 of the 4 only had small printing capabilities and that was to print snipes, censorship material and press material. In other words, they received their US posters like a regular NSS warehouse and applied the local censorship snipes on them for distirubution. That’s why you normally see the US ratings box covered over. Only one branch had full printing capabilities.. the Montreal branch. And that was because they served a very high French public, so they printed the French versions.