I picked up a gascanteen and a gaslamp and put them together. When I switched on the lamp in my hands, it shines, but there is no illumination in the area.
I put the lamp into my bagpack and switched it on. There where I stand the illumination I missed appeared. But without a lamp in my hand. Then I went a few steps away from that spot and the illumination was on that position, where I switched the lamp on in my backpack, or jacket, or trousers.
So I moved to another place and took it into the hand. It shines but no illumination in the area. Again in the backpack, jacket or trouser, I switched it on and the area was illuminated, but only there where I switched it on. I could switch the spot where I put the lamp in pocket on and off. Funny! Could be a nice trap on nightserver for making other players wondering around what it is, while I aim and shoot! Muahahahahaha.... :D