The air control and the tap valve protruding through are odd to me. Being a downward pointing mantle is of interest but so is the Marla and a few like it. The air control is more like a gas lamp thing but it could also just be a very early type lamp. I am definitely not suggesting it is a franken lamp, what I am saying is that it is an interesting lamp.
The mantle to fit would have been something like this. The chances of getting one are slim at best but making an adapter to fit other mantles should be easy enough.