Shown here from 75 years ago is a blackout light bulb, manufactured by the Wabash Appliance Corp., 335 Carroll St., Brooklyn, NY. The bulb provided a beam of blue light that was projected downward, for use indoors during wartime blackouts. The inside of the 25 watt bulb had a silver reflector to hide filament glare and direct the beam downward.

It is shown here mounted in a socket, from the January 1942 issue of Service magazine.