Perhaps all the upper half was once the cover which was lifted by the ring and edge was fixed to the bottom part later?? If it was a burner, then it should have something to pick and carry it,most practically two facing each other in the middle edge,not? The small ring on the top would be very weak and uncomfortable to carry an oil filled burner, and as it would be expected to get hot while burning or even wet with oil, one would not wish to hold it by hand directly on the main body.In fact even if it was a sahan,it should have something to carry it comfortably but it doesnt..
