This single coiled tungsten filament light bulb was manufactured from 1919 onward as a tip-less bulb. By coiling a very long tungsten filament, the effective length of the filament is increased (in order to increase the wattage) without taking up more space. Its development was the next step resulting from Dr. William D. Coolidge’s
hard work in creating a bright, glowing ductile tungsten filament. It looks more like the standard household light bulb of today and is the last phase in the evolution towards today’s modern, economical and popular incandescent light bulb. For further dating, if the bulb should have the MAZDA trademark and the GE monogram on a label or sticker [see A44a?]
affixed to the outside surface of the bulb or to the stem tube inside the bulb, the bulb dates from 1919 until 1926, when labels were discontinued and etched trademarks first appeared. If the bulb has MAZDA, GE monogram, wattage, and voltage etched on the top of the bulb [see A44]
, the bulb dates from 1926 to 1945. If the bulb has GE monogram, wattage, and voltage etched on top of bulb but WITHOUT the MAZDA trademark, which was discontinued in 1945, the bulb was manufactured from 1945 onward.
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