Osram SO/H Sodium Vapour Discharge Tube
This SO/H sodium vapour lamp was manufactured by the General Electric Company of England under their Osram brand name in November 1965.  The lamp is in mint unused condition and has all of its original packaging intact.  This includes two small pieces of asbestos paper placed between the arc tube and porcelain cap to prevent scratching the glass near the delicate seals, and the whole lamp is wrapped in heavy tinfoil sheet to safely contain the sodium in the event of breakage.

This is one of the last SO/H type lamps that was manufactured, having been made at the company's Shaw works near Manchester, England.  Most of its constructional features are shared with the more modern SOI type lamps which were being manufactured at the same time, so it exhibits the more recent electrode assembly which makes use of a beehive-shaped cathode coil complete with magnesia insulators to offer some protection against sodium attack at the weak glass-to-metal seals.

The glass type used is almost certainly an X96 barium-aluminoborate lining flashed onto the inside of an S97 soda-lime glass tube, as manufactured at the GEC's Lemington glassworks.  As a result lamp life is considerably extended from the reduced argon cleanup rate of this glass, and the sodium remains in several small globules where it was originally located because this glass offers much better adhesion to liquid sodium.  Although the lamp is new and therefore no sodium staining is apparent, this glass type would turn brown at a much slower rate than for earlier SO/H lamps so the lumen maintenance of this design is also greatly enhanced.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 45 Watts
Lamp Current: 0.60 Amps 0.54A Starting current
Lamp Voltage: 80 Volts 200-250V Mains voltage
Cap Type: BY22d Mycalex Insulator
Bulb Finish: Clear Soft glass arc tube
Bulb Type: Inner: TU-16 x 40 Outer: T-50
Overall Length: 525 mm 20¾ inches
Light Centre Length: 290 mm 11½ inches
Arc Length:
Electrodes: CCC-4 Black Tungsten BCT emitter
Atmosphere: Na | 98.5% Ne, 1.5% Ar Outer: Hard Vacuum
Luminous Flux: 2,800 lm (Lighting Design Lumens)
Luminous Efficacy: 62.2 lm/W (Lighting Design Efficacy)
Colour Temperature & CRI: CCT: 1700K CRI: Ra-44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Burning Position: Horizontal ± 5°
Rated Lifetime: 6,000 hours to 70% survival
Warm-up & Re-strike Time: 11 minutes Instantaneous
Factory: Shaw, Oldham England
Date of Manufacture: August 1972 Date Code DH
Original & Present Value: £3.40 (1976) £16.39 (2005)
 
References: 1) Osram-GEC Lamp Catalogue, 1959-1960.