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This is a tip-less fully outside frosted light bulb with a drawn tungsten filament. The frosting was created by dipping the lamp into a tub of acid to etch the hemispherical top (while the neck and sides were left unfrosted) until the desired thickness of frosting was obtained and probably began in the 1880s.  Because of the resulting rough surface, these exterior frosted lamps were structurally weakened and thus easily broken.  The surface was also prone to collecting dust and grime, which reduced the light output and made it difficult to clean.  This bulb was manufactured from 1919, the year tip-less bulbs were first manufactured, until 1925 when outside frosting was discontinued and interior frosted lamps were introduced.

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