i brought this at a carboot today because it came with something else i wanted. just wondering if any of you guys know what it is? it has a large copper coil inside and the red bar slides into it from the side of the box, this feels to have a iron center so that would make the coil an electromagnet, the thin metal bar seems to be tuneable for how quickly it vibrates from side to side (when you flick it but id guess the electromagnet would attract it and then it losing contact with the bar it touches would break the circuit). any guesses