I don't think anyone has come up with a conclusive answer as to what the tabs represent. Some think it's to maintain an air gap when the lid is stored upside down on the pot. But what's to keep the lid from being stored right side up? On many sizes, the tabs don't prevent the lid from sitting flush with the pot rim anyway. I always wondered if they weren't some manufacturing device. The reason they're called Tite-Top is the joint on the lid and pot are ground to create a better seal. On the lid, this would likely have been achieved by mounting it on a spinning machine. Since the lip would have to be kept totally clear to apply a grinding head, the only attachment would be the handle. Perhaps the tabs were a way to prevent the handle from being torqued and broken off. I could be totally wrong, but it's a theory.
