What in the world is that? A part of a train?

Man, this looks like something you would find on a train.  Could it possibly be a knob that adjust something like steam pressure?  Oh wait…I know!  It’s a door knob!  No?  Then what is it?

Maybe you know what it is.  It’s certainly a knob.  But of what, exactly?  Could it be from a tool?  Or possibly even from a car, like an old turn signal?

Any guess is greatly appreciated on what this could be, and the item will be revealed next week!