Blackout lamp, ca. 1940
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During World War II, especially along coastal areas, blackouts were issued periodically where all street lights were turned off, cars and truck lights were dimmed and lights turned out in homes so that enemy bombers or ships wouldn't have light to identify targets.
Blackout lights were developed so people could still have some light. This bulb, in the shape of a radio tube, has a mirror coating on the inside to help focus the light to the bottom.