Reader Michael found this lid at a thrift store.
Note the hole. I’ve never seen another Revere Ware lid with a hole like that; Michael found two. Given that the holes were in different spots on each lid, and Revere Ware is not known to have put any holes in their lids, these were probably added by a previous owner.
The benefit of having a hole in the lid is it allows for pressure changes inside the pot when there is a boiling liquid, which keeps the lid from rattling on the pot. Pretty useful, really.