What is this Brass oil lamp used for?

I found this brass lamp the other day and have know idea what the heck it is. Seems to be set up for oil and had a place for a wick, and a small chain holds a pin for cleaning the wicks - I'm guessing.
The oil pot can rocks/ pivots on screws that are attached to the stake , that made me think it might be for a boat. At the end of that stake is a barb, maybe it's for staking into rock so you can mine without holding the lamp.
I have know idea. I hope one of my fellow collectors can tell me what the sam hill this thing is.
thank you for your time,