It is what some call "bullet shaped" and threadless. Patented July 25, 1865. There are many imperfections in the manufacturing of this item. Deep swirls in the glass on one side almost erases the raised lettering "55 FULTON ST." circling the dome top. The patent date also encircles the dome but letters are very faint. There is what looks like a deep crack starting at the swirling glass and running about half way up the dome on one side, but can't be felt either on the outside or inside of the insulator, which leads me to believe that this too was done at time of manufacture. There is a small smooth chip on the very bottom of the base and a small ding on the topside of the dome. This was found many years ago on a now uninhabited island on the Outer Banks of NC that was captured and occupied by Union Troops during the Civil War. There has never been electric power on the island, so is it possible that this was from a telegraph pole and manufactured for that purpose alone. ...http://www.in-glass.com/direct/7284BFLtAqua.htm ... $378.00 ... for other great items see ... http://www.in-glass.com/direct/ ..