Just before the Polaroid lawsuit was settled, Kodak was working on a slide film (really a 'lantern slide') and projector. It was peeled from the picture unit (like the Trimprint film) and there were plastic slide holders to hold the film. To the best of mu knowledge, it never hit the market (although there were external trade trials). Loosing the Polaroid lawsuit ended the product.
A year or so after leaving Kodak, I was invited to visit Polaroid. I had an hour (or so) discussion with a senior manager about to retire and we swapped stories about projects. When I mentioned the transparency film and projector, he went over to a cabinet and pulled out a small projector and asked "Like this?"; it turns out Polaroid also worked on such a product.
But Kodak made an instant slide film (photo in post #47 ). Which format had the intended one you are refering to?
Polaroid did made 35mm instant slide films (color an monochrome). What kind of slide material had you been shown?