With the door hinge on top, these are most likely truck. The mounting method is usually seen on electric lamps but not out of reason on truck lamps as some trucks were still being sold with gas lamps well into the 1920s. Many trucks did not have starters and generators, truckers were expected to be big guys who loaded and unloaded the truck and would have no problem with a hand cranked engine. These may also have been originally painted all black. It was functionality not styling on commercial vehicles.
Your lamp has a mounting bolt at the bottom. The same lamp was offered with fork mounted fittings. I agree with all Layden has said. I have never been able to link a manufacturer to them. Later versions were offered with steel tops and doors. White trucks used them a lot. Probably an option on Macks and many others.
Dennis, you are correct. A Pair is a very good thing to have. Singles, not so much. As they were available in the mid teens to the late twenties, they could have been installed on almost anything. And were.