David, thats pretty much correct. There were several different companies that made these style of lights and several different styles.If they illuminate from the bottom, they had a lens and snap clamp of some kind, and a hole to vent them. If the lens was not installed a small weep hole could not get rid of the water, ice, snow, or bugs and the bulb would have a very short life. Most of the lights that did not come with a lens were used to illuminate from the top of the pole/sign downward, and did not need a lens, or a hole to let water in. At almost every swap meet I have been to you can find parts for these lights.