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This type of bulb has its carbonized split Japanese bamboo filament attached by carbon paste joints.  It also has a copper-shelled threaded base with two or three threads and one straight-sided copper contact on the bottom of the base over a plaster of paris insulator.  The base is cemented to the neck of the bulb by a thick ring of plaster of paris between the bulb and base.  Bulbs with this type of filament attachment and particular base were manufactured from 1886 to 1888.  This particular bulb was made in 1886.

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