Stories waiting to be told

To our delight in the cellar we came across this mechanical and physical wonder. We've been told it is a gas light arm -- the gas would be run through the house in the walls and in each room there would be these gas lights. Does anyone still have these in their walls? I presume they do not function any longer (would not want to try), but can anyone give us more detail -- or tell us stories -- about this lovely contraption from a previous era?