One of those may have been involved somehow, but there was definitely a rattling ball in there you could hear if you shook it. I'm having trouble finding images

One of those may have been involved somehow, but there was definitely a rattling ball in there you could hear if you shook it. I'm having trouble finding images of how it worked, but many car forums discuss the "small gold bearing in a cylinder" that's used in the fob. Unfortunately, Google wants to show me links to buy stuff. It's getting impossible to find "standalone" web pages these days.