This lovely old theatre light dates back to somewhere around the 1950s and was built in London by a company called Stage Electrics (no relation to the modern day production equipment suppliers of the same name) and sadly that’s about all the history that I can dig up on it.
This type of light is used in theatres and concerts to provide a nice soft-edged pool of light on the stage. They have a mechanism which allows the bulb to be moved relative to the lens, which lets you “zoom” the light output. This is still fully working, so you can choose whether to go for a soft, wider pool of light or to focus the beam down and see the pattern of the bulb’s spiral filament on whatever it is that the light is pointed at.
Originally it was painted all black but it’s now been given a shiny new pale blue paint job. Shiny metal highlights from the chrome electroplated parts and internal silver foil bring eye-catching shine and detail. It has been carefully rewired with a new modern ceramic lamp holder but apart from that all the other main parts are original.