ID UV erasable PROMS used on an IBM PC board?

Years ago when I was at Intel, they would take EPROMs that had only a few defects and attempt to program them with specific applications. They would then usually paint the window black and put on that particular product number. When we needed EPROMs in the lab, we would take a pile of these that were no longer used and scrape the paint off the window. Some would take the desired program and some wouldn't. I suspect that they can fuse identify specific bad EPROMs to use for such harvesting. The fused value may be laser blown as well. My guess is that that is the reason for the different ID number. If it will take pre-programming with a particular data, it is worth harvesting. This way they can find value in an otherwise unsellable product. I doubt the harvesting methods have changed much over the years.