Hello Iconers;On one of my spring hunts, i was out in an old abandon sawmill/telegraph railway ghost-town and was rooting around, finding old insulators and glass bottles, and come across this porcelian (face-plate ) marked Edison U,S.A,,it 7 inches in diameter and it, s got a threaded bolt through the plate .It, s had some electrical purpose,,looking for any information on what it was used for ..thanks Andy .... Thanks, Malcolm Steve and Martian.. Battery jar top seems to be the consenus....