Bumix "Jupiter" Mercury-Tungsten
It must initially be stated that the precise purpose and application of this lamp remains unknown.  Clearly it takes the form of a high pressure mercury vapour lamp, and it incorporates a tungsten filament - but not of the type that would generally be employed as an internal ballast in the case of mercury-blended lamps.

The unusual feature of this lamp is that it is equipped with a special three-contact screw cap which enables the arc tube and the filament to be lighted independently.  The individual voltages of the filament and arc tube are marked on the wrapper, the filament apparently not being designed to act as a ballast for the arc tube as its voltage, 210V is too high to act as a ballast on normal mains voltages. It is therefore curious to wonder why the lamp needed to be fitted with a cap which enables independent lighting of the filament and arc tube.

One possibility is that the lamp was created as a variable colour source.  The wrapper specifies the use of a special Bumix control gear for the lamp, which is perhaps able to vary the current to both the arc and the filament and effect a change in emitted light colour from the warm-white incandescent output to a cool blue-white mercury vapour spectrum.

Interestingly despite the high loading, the arc tube in this lamp is fabricated from aluminosilicate hard glass rather than the traditional quartz material.  Seals are fabricated to solid rods of molybdenum, and no auxiliary starting electrode is provided.  Little is known of this East German manufacturer other than that the various ratings of these kinds of lamps were each named after various celestial bodies.
Manufacturer: Bumix
Lamp Power: 605 Watts
Lamp Current:
Lamp Voltage: Arc Tube : 140 Volts Filament : 210 Volts
Cap: E40d/45 Brass + Porcelain insulator
Bulb Finish: Clear Soda-Lime
Bulb Type: K-130
Overall Length:
Light Centre Length:
Electrodes: Backwound Tungsten with triple carbonate emitter
Atmosphere: Inner : Argon Outer : Nitrogen
Luminous Flux: 13,500 lumens
Luminous Efficacy: 22.3 lm/W
Colour Temperature & CRI: CCT: CRI:
Chromaticity Co-ordinates: CCx: CCy:
Burning Position Vertical cap up
Rated Life: Not Published
Factory: Berlin, East Germany
Date of Manufacture: Circa 1950
Original / Present Value: Unknown