I converted an old style lantern into an LED torch. The battery life is now measured in hours and I don't have to worry about carrying spare bulbs or finding 19th century batteries.
Step 1: Torch Dissassembly
To get the batteries and LED assembly I took apart a cheap silver torch, which cost me $4.
The PCB holding the LEDs was soldered directly to the metal barrel of the torch. Holding a jeweler's screwdriver on the joints and hitting it with a rubber mallet allowed the assembly to come off quite easily. Actually I was pretty impressed with the quality of the torch, so I've bought half a dozen of them.
Step 2: Wiring
The lantern is pretty old. It takes some weird large prism shaped battery I've never seen before. I'm not sure if it's an old mining lantern or for the front of a bicycle.
The switch is the large bolt on top. If you turn the bolt a few times it presses down on the contact and makes a connection to the body of the lantern. The design is clearly from before the era of cheap plastics. The switch mechanism uses strong cardboard for insulation!
I soldered a wire to the contact (I had to file it first to make it stick). and another wire to the body. Then the battery was wired up so that the switch made a series connection, and the two wires to the lamp were passed through the hole to the front.
I soldered the lamp wires directly to the PCB assembly and insulated them with a bit of tape. Some hot-melt glue helps hold the lamp wires in place and prevents them from being seen from the front.
Step 3: Finished.
With the wires in place I put everything back together.
So now I have a steampunk looking lamp, with the double bonus a many hour long battery life, and not having to worry about replacement bulbs.