These were quite common during the 1890-1910's. They typically had a CD 280 insulator on a bracket which screwed into the fixture section. Joe Maurath has one that is in working condition that lines his driveway. It was reassembled using parts from several other lights but finally he got this one complete! Photographed during the height of the brief blizzard with strong winds we had here near Boston during 12/05. Other photos that I have posted here show this fixture in much better New England ever-changing weather!