I bid on an ebay auction for "VINTAGE NATIONAL SEMICONDUCTOR FILM PHOTO ETCHES". It looks like they are just overhead transparencies for a class, but they are still pretty cool. They are marked DM7880C, so I looked up the datasheet, and that's a 7-segment decoder driver, like the 7447, but with the segments stored in ROM instead of generated by logic gates.
Some of the layers are obvious, but I'm not sure what some of them are. I was hoping I had a chip here to decap and take pics of, but I couldn't find one.