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This is a tip-less drawn tungsten outside bowl-frosted lamp.  Bowl surface should look frosty and feel coarse and abrasive, somewhat like that of a fine sandpaper.  The tungsten filament is threaded numerous times between two levels of several wire supports attached radially around the upper and lower portions of the glass button rod (about 3 to 4 at both top and bottom).  (Tungsten filament has a very low electrical resistance so that it is very long (about two feet in total length) and thinner than a carbon filament.  These drawn tungsten filaments were eventually replaced by the shorter coiled tungsten filaments about the same year that the tip-less bulbs came out in 1919.)  The frosting was created either by sandblasting or 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.  This method of frosting 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.  Bulb should have the MAZDA trademark and the GE monogram on label or sticker [see A44a?] affixed to outside surface of bulb or to stem tube inside bulb.  These bulbs were manufactured from 1919 to 1925, when interior frosted lamps were introduced.


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