Thanks for the link
What a neat piece of kit that old coil is ! I had planned to make something similar to this before you sent me this. I've ordered a reed switch in a glass tube, it's the heaviest duty one I could find, so hopefully this should last longer. It's normally open contacts I'll close with a small magnet, and hopefully the field from the coil will over power the permanent magnet and open the contacts.
I have a 1/2 pound real of 24 gauge magnet wire for the coil, it's 'q' factor is not too high, but I understand that a high voltage coil has to be long and narrow for best results ?