For the info from Wikipedia, which contains a lot of the subjects being discussed here:
Tenifer et. al.
Notice that there is only one "n" in Tenifer
And the US-made versus Austrian-made slides are confusing some people, as in there is no EPA influence in Austria.
I think it is quite likely that early Gen 4 frames could have been matched up with the last of the Tenifer processed (notice I did not say "finished") slides.
Bart Noir