LOL, These are still used! I work in a prison and we use a brass disc with our name hand stamped onto it. Normal issue is 10 per person to account for equipment. We call them chits.
For my line of work, we use three sizes of disc. Large would be a key ring number. Small is a key count. Medium (the personal issue) is about anything else.
That is not to say people haven't added their own twists and personalized the system. Some control room officers delight in scarring chits by whatever means. I have personally spent time painting a chit with pink fingernail polish and wiping the remaining excess. I have seen one girl with a disc that was raised as a nipple (I thought it was a shield, but she corrected me). I've also seen teddy bear and Star Trek shaped discs. Aluminum and laser engraved tags are seen, but not common. Depends on the facility that made them. Brass discs make up most of it though.