The light bulb that you can find in the niche of the Aft Lower Window Liner’ to the bottom of the various circuit breaker panels to illuminate.

With a lot of waste of aluminium and wood is this light fairly easy to build and serves just as decoration. It is in my cockpit, not operational (dummy).

Information and pictures are to be found at the following link:
http://www.flightdeck737.be/hardware/platform/window-liners/side-aft-lower-window-liners-capt-en-fo/