This probably would not be helpful with tracing the origin of pirated tapes, but you could identify recovered prints and get the source theatre/depot.

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It would be great! Every single print would then have it's own special on-screen code different from all the other prints! Plus, there wouldn't be any of that annoying CAP code marks that resemble dirt on the film!!! Yes, this would be perfect, as there aren't enough lab splices within prints as it is.

(Of course I'm kidding. The CAP code is probably the best thing given the circumstances.)

Video cameras are sensitive to wavelengths that human's can't see, either. Further, they don't necessarily have to couple with any color that's visible on the TV screen. (IR light looks blue in a video cam. -- Counter-intuitive until you think for a while.)

Just supposing here but if you built a layer into the film that was sensitive to only a very narrow band of IR/UV light and coupled that to a dye that filtered a wavelength that TV cameras could register but couldn't display, you could put anything you want on the film. For instance, you could put vertical stripes down the film that resemble bar codes in the supermarket. They could be recorded on video tape but since they are just outside of the CRT's ability to display them, the only way to see them would be to play the tape through some sort of video analyzer. An oscilloscope, for instance.
The scope would display a pattern of "pips" like this that correspond to the location of the lines in the "bar code", like this.

--------^---^------^----^^----------------

This could be throughout the whole length of a reel (or reels) and there would be no way of removing it or even finding it unless you scientifcally analyzed the film.

I suppose the flaws with this idea would be that someone could power off the IR LED array, and there may be filters available for cameras to block stuff like that.

There's no screen to put IR LEDs behind. When they showed film (yes, I'm that old) they projected directly into a camera. Used a light source and everything!

I'll try and get him to register here. He's a computer geek now, but he was once a top notch TV guy.

AND! He's older than me so I'll feel better too!

Russ