Yep... it's an old fruit jar lid, zinc with a porcelain liner. This type of lid was invented by Lewis Boyd, who filed a patent for it in 1869. Similar lids continued to be manufactured in huge quantities for many years thereafter. Here's a link to the patent:
Rings off like a penny signal, then it is 8 to 10 inches deep...trash dumps...they stink.... but at least you are hunting in the right places for older stuff....jgas
They might be common, I do have a few myself. The one I dug this past week was a new one for me...I was shocked when I saw the Iron Cross on the lid. After searching and reading about it, I said to myself it's a first of it's kind for me, so it's a keeper.