This is a projector bulb with a very unique, distinctive look. It fits into many projectors including: Bolex, Eumig, GAF, Argus, Bauer, Chinon, Fuji, Hanimex, Lenco, and others. This projector comes in 3 different styles. They are the Diver Dan (shown here), the tubular, and the external reflector. They all function the same and are interchangeable because the bases are alike.
Besides Diver Dan, this bulb has also been called "The spaceman lamp". It is simply a normal projector bulb with an unusual shape. I have two of them: One is made by GE, the other by Toshiba. There are slight differences between them: The GE bulb's interior plating has a more gold-ish color, and has a larger "head". Both bulbs were made in Japan.