Bally introduced the "lock ring" in 1956, as far as I can tell. They used lock rings on their line of bingo games as well as some novelty games such as Skill-Roll. I'm not sure when the rings were discontinued. If you've got one you'd sell that isn't bent or rusted, I'm interested. The part is circled in red on this flyer for Bally Key West. I just need the ring, not the lock. Thanks.