Hi Mike,
I believe that this is a WAGNER Maislin Kettle, circa 1915 - 1924.
By virtue of the markings... WAGNER
SIDNEY
O
I think I see a '4', which would indicate a 4 quart.
The bottom pitting makes it tough!
(Now I'd like to see what Russell thinks also, as I debated between this and Yankee Bowl, but the shape, and design features of the tab over the ring look to be Maislin).
The lid is also Wagner. I suspect the lid may be a Dutch Oven Lid. The old Catalogs do not indicate that lids were ever produced for the Maislin Kettle. So it would be a marriage.
Now I am seeing a strange surface texture, on both the kettle and the lid, that I saw on your Griswold 3 in 1 skillet and Lodge lid. The texture is not normal for these pieces or for any Cast Iron cookware produced by Wagner and Griswold.
It is not clear whether it may have been caused by acid exposure (e.g. too long of a soak in Vinegar solution), or some sort of abrasive used to clean them or ???
Given the age of these items, it is difficult to determine what may have happened to them in their lifetimes... many years ago.
Now, we can wait for Russell and others to stop by also!