Philips HO 2000 Medium Pressure Mercury
Early mercury lamps manufactured by the Dutch Philips company were split into two principal families. The HO types employ an arc tube of hard glass, while the HP types make use of a quartz arc tube. These two categories are directly comparable with the British MA and MB types respectively.

It was furthermore customary in most of continental Europe to rate lamps according to their output in dekalumens. Thus this HO2000 lamp is a 20,000 lumen device, and draws 450 watts. There is also a smaller HO 1000 (265W). European lamps have different electrical ratings than rest of the world, and require different ballasts.

The arc tube in this lamp is fabricated from aluminosilicate glass that has been blown into a mould to form the desired shape. The end sections around the electrodes are of reduced diameter, and also painted with a platinum heat-reflective layer. The purpose is to increase the temperature here slightly, and attain a faster run-up time than usual.

The electrodes are modelled on the design of American lamps of this era, and consist of a beehive shaped coil made from heavy gauge black tungsten wire, coated with the usual trimetallic oxide emitter of barium, strontium and calcium. They are welded to a stout molybdenum T-piece, which is sealed directly through the ends of the arc tube. A third auxiliary molybdenum ignition electrode is situated 3mm from the main electrode at the cap end of the lamp.

The arc tube is supported resiliently between a pair of punched steel discs, and suspended in the hard glass outer bulb with the aid of tightly spiralled springs.
Manufacturer: N.V. Philips Lamp No. 57102G
Lamp Power: 450 Watts
Lamp Current: 3.25 Amps
Lamp Voltage: 140 Volts
Cap Type: E40s/45 Brass + Vitrite
Bulb Finish: Clear Borosilicate hard glass
Bulb Type: T-51 T-16 in eighths/inch
Overall Length: 295 mm 11 5/8 inches
Light Centre Length: 180 mm 7 inches
Arc Length: 152 mm 6 inches
Electrodes: CCC-4 Beehive coil Trimetallic oxide emitter
Atmosphere: Inner: Hg | Ar (1 atm) Outer: Nitrogen
Luminous Flux: 18,000 lm (@ 100 hours)
Luminous Efficacy: 40.0 lm/W (@ 100 hours)
Colour Temperature & CRI: CCT: 5400K CRI: Ra 6
Chromaticity Co-ordinates: CCx: 0.337 CCy: 0.421
Burning Position: Vertical ± 45º
Rated Lifetime: 6,000 hours (to 50% survival)
Warm-up & Re-strike Time: 4 minutes 15 minutes
Factory: Eindhoven Netherlands
Date of Manufacture: 1st Quarter 1956
Original & Present Value: Unknown