I think Ektachrome 64T was introduced between '89 and '91 but I'm not sure about the year
and as for 160T, well I've seen some pictures claimed to be shot on Ektachrome 160T as early as 1985, but I don't know if that is the same film that is being sold today
I seem to recall there was a Kodak ASA 160 tungsten Super 8 movie film from before 1984, but I'm not 100% positive of that. Whatever I'm thinking of, though, it was hard to find.
I shot Ektachrome 160T in 1983 or 1984, and remember having it pushed one stop. The alternative would have been Scotch 640T, which was pastel and amazingly grainy. Amazing how finding old pictures from High School make you *not* miss that age.
I can't find any information one way or the other. The tech pubs were recently revised, and all I can find from my old slides are that they were E6 process. Sorry; it's probably, like Tri-X, been slightly modified because of changes at the processing plant, but I'm afraid you're going to have to go to Kodak for the definitive answer.
The Kodak Professional Ektachrome 160T Film of today is basically the
same product offered in the 1984 time frame. No product performance
upgrades have been done since. However, that's not to say that
manufacturing changes through the years may have caused some changes in
product performance. "
There you have it. Within manufacturing tolerances, it's the same film.