I haven't found anything that definitively indicates whether Kodak sheet film followed the same edge code dating system for their sheet film as they did with 35mm (much more documentation for 35mm, perhaps due to an active movie film preservation community), but did find the article below regarding notch codes for nitrate vs acetate sheet film. From what I can see in the image posted, the "U" notch code identifies the film base as acetate (which correlates to what appears to be word "safety" after Kodak on the edge printing). After that, it looks to me like two triangular notches, which IF they match up to 35mm edge codes, would indicate possible years of 1941 or 1961 for the manufacture of the film itself.
After those mental gymnastics, if anyone knows of a definitive guide to dating sheet film, or can verify at least that Kodak followed the same protocol as with 35mm but with the addition of the notch for acetate vs nitrate, I would very much appreciate a point in the right direction. I've handled a lot of sheet film over the years, but unfortunately haven't kept good enough notes to easily research the answer myself.
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