I have found 3 or 4 of these over the past few years. They are a canning jar lid I know. But they are only about 3/4 size of the regular mouth lid beside it. My mom says they fit a certain products jar commonly purchased at the store, so the jar could be reused. BUT she doesn't remember the product or the specific number of the lid. Any help?
I have seen a few of these Rob, but I'm sorry I can't help with the exact ID or use of these. Neat find. I think I may have one of these laying around. If I'm not mistaken some of these had a small inner porcelain disk on the innerside of the jars lid. I almost forgot to add: I'm old, but not a home maker. Lol