I say "probably", because I'm not sure if there were earlier versions of such films, designed for earlier motion picture processes.
before Process ECN2 there was of Course Process ECN. I think the last film to use that was teh second coming of 5254 (the first 5254 was a much older film also using ECN)
some key items from
https://www.kodak.com/en/motion/page/chronology-of-film/
(1950: EASTMAN Color Negative film, 5247. 35mm. Daylight, EI 16. First Kodak incorporated-color-coupler camera negative film. Replaced by 5248 in 1952.)
(1968:EASTMAN Color Negative film, 7/5254. Tungsten, EI 100. Replaced 5251 (EI 50). Image structure equal to 5251. Discontinued March, 1977 (E). Oscar® Awarded -- (41st Academy Year) Class I. Scientific or Technical Award)
(1974: 5254 RETURNED TO PRODUCTION UNTIL 1976. ! ! ! )
(1974: EASTMAN Color Negative II film, 5247. Tungsten, EI 100, Daylight 64. Sharper/finer grain than 5254 (EI 100) (E). Process ECN-2 (new process). EDTA bleach. Paper given 1972 SMPTE.
the page is mostly written in Movie Geek Speak. BUT almost all the changes in Movie film are listed - for example (1959: EASTMAN Double-X Negative film, 7/5222. Daylight, EI 250. Tungsten, EI 200 (E))
not to metion the Big Buzz on these pages (2007: KODAK VISION3 500T Color Negative Film 5219/7219 (EJ. The first in a new family of films is everything you love about KODAK VISION2 Films-the overall look, the image structure- with a host of added improvements.)