identify your lightbulb > bulb identification key

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“This is a clear three-watt lamp (not a lamp with a rating of 3 watts) also known as a three-way lamp.  The General Electric three-way lamp was first introduced in December of 1933.  Used in a socket that is provided with multiple switch, the lamp could be operated in one of the three different wattages supplied by the filaments, with the filaments operating either alone (to give either one of the two different lower wattages indicated on the bulb) or together in order to provide the highest wattage indicated.  Three-way bulbs were actually conceived and employed long before 1933, but it was General Electric that first manufactured them for the general public use.  For further dating, if the bulb should have MAZDA, GE monogram, the three wattage ratings, and voltage etched on top of bulb [see A44], bulb dates from 1933 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, bulb dates from 1945 onward.

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