not smooth on the inside, no detail other than a few ribs
no wax residue on mine. mine are cast iron so could it be a foundry mark? one's I've seen are usually numbered and have good detail. Mine show no signs of being hit with a hammer or mallet to mark something like leather.
To me they look like they maybe some type of holder? wax holds the "part" to the holder?
Glad someone else has one so I know they are not a local thing!
Chips you are not in Southern Illinois are you?