I have a Model T valve stem cap and that is not one. Like they already mentioned it is a valve stem remover. It could be a cap with a valve stem remover on top but I think it is just an old tool. Also like mentioned the valve is called a Schrader valve, and it is still used on today’s wheels. I'm a mechanic and have a few of them, different styles, just do a google image search and you'll see.