Honestly I'm having difficulty picturing what you are asking about. Could you post a photo? I have never seen any commercially canned foods with 2 piece canning lids. I have seen ones that come with what are called 1 piece canning lids or "button tops" lids. They are quite common although not recommended for home canning. And yes they form a seal with the jar rim.

Dave

http://www.fillmorecontainer.com/Single-Piece-Canning-Lid-G70-Gold-Button-P276.aspx

That is the one! Thanks!!

Yikes! I read the description on those lids and it states they are for hot fill only (not for water bath or pressure canning). Are there really that many people doing open kettle canning that there are lids of every color specifically for that method?

No they aren't hot-fill only. They are used for things like jellies and jams that are BWB for short periods of time. Note the description says "not FOR LONGER WATER BATH (> 15 minutes) " so no more than 15 mins.

Can't say how many people may be using them for home canning since they are expressly NOT recomended by NCHFP. I suspect there are still far more of the great-grandma-did-it-this-way bunch still doing open kettle canning than there should be. But if they are using them then technically that is fine for short BWB use.

As for commercial canners using them with their very different equipment and different guidelines, I can't say. But it still doesn't mean they are doing open kettle canning.

Dave