This would be an insulator go-with. A few of these were made back in the 1970's (?) in the Millville, NJ area. Two men, Bob and Tom, who worked for the Kerr glass company made them. It was certainly made to look like an insulator. It has a small threaded pinhole. There is a very tiny base flake and some light roughness around the base edge where the glass was slightly over poured. Hard to put a value on this one. How about $150.00 shipped.