Peter Carlin the author wrote me back, he couldn't help out, but it was nice of him to reply so quickly.
Hi Dave, I hate to disappoint but my description of that session was based on footage shot by Gary Rebo during the 70s and what I saw either didn’t have any date info on it or didn’t matter to me enough to track. I’d guess the former being as omnivorous for info as I could be during that project. But that work was a long time ago now and my files are up in the attic somewhere, I think. So I feel like less of an expert on this then you’re probably looking for.