GE Tantalum Filament 25W of American Design
Soon after the invention of the tantalum lamp in Europe, the news caused great concern among American manufacturers, who had performed no significant research of their own on metal filament incandescent lamps. The risk of losing their dominance to superior imported lamps was high, especially for General Electric, which together with National had operated a near-monopoly in the Americas since 1901.

In 1904 Siemens & Halske offered GE the American rights to its invention for a high price, but GE declined owing to the reduced life of tantalum filaments on AC circuits. However such was the level of threat that GE eventually conceded, and on 10th Feb. 1906 for a payment of $250,000, secured exclusive American rights for itself and National to produce the lamps on a royalty basis. All American-made lamps were produced with tantalum wire sourced from Berlin.

This situation caused enormous stress within GE, because its research laboratory had been established precisely to maintain a leadership position which would avoid paying competitors for the use of lighting-related patents. To make matters worse, the situation was repeated when it again had to license sintered tungsten technology from the Europeans. However its high price meant that GE's tantalum production continued until 1910, after which Coolidge's development of ductile tungsten entirely displaced both tantalum and sintered tungsten from the USA market. This particular lamp has a rather unusual filament formation, with three instead of the usual two sets of carriers. Its purpose is perhaps to improve vibration resistance, or to achieve a mount of shorter length and higher brightness than with ordinary tantalum lamps.
Manufacturer: General Electric Co. of U.S.A.
Lamp Power: 25 Watts
Lamp Voltage: 116-120 Volts 120V nominal
Lamp Current: 0.21 Amperes DC operation only
Cap Type: E26s/25 Brass + vitrite
Bulb Type: SA-58 SA-18 in eighths/inch
Bulb Finish: Clear Soda-lime glass
Filament Type: S-17 Diamond Cage
Atmosphere: Vacuum Red P Getter
Luminous Flux: 150 lumens 12 CP
Luminous Efficacy: 6 lm/W 2 watts per candle
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: CRI:
Chromaticity Co-ordinates: CCx: CCy:
Rated Lifetime: Approx. 1000h on DC 300-500h on AC
Burning Position: Universal
Overall Length: 127 mm 6 inches
Light Centre Length: 83 mm 3ΒΌ inches
Factory: Central Falls, R.I. U.S.A.
Date of Manufacture: February 1909 Date Code: e11 145
Original / Present Value: Unknown Unknown
 
 
References: 1) American Tantalum Filament Lamps, website of Ed Covington (Web Archive)
2) The Electric Incandescent Lamp, E.J. Covington, NELA Press, 1998
3) Networks of Power, T.P. Hughes, John Hopkins University Press, 1993 pp. 167-168
4) The Making of American Industrial Research, L.S. Reich, Cambridge University Press ISBN 9780521522373 pp. 73-74