These are Wabash Indoor Blackout Bulbs, and they saw use during WWII. These are American bulbs, but European blackout bulbs also exist (in Germany they were called Air Raid Lamps, "Luftschutz Lampen"). Their purpose was to create a minimal light source to be used inside homes during air raid alert "blackouts", in which there was reason to believe there was danger of an air raid. When this happened, all normal bulbs had to be turned off, and these bulbs had to be used instead. The idea was to make it more difficult for enemy aircraft to locate their targets. I heard a story about these bulbs from an eBay seller, he claimed that if patrolling troops saw light coming from your home during a "blackout", they could shoot out the source. (I haven't verified this). I know for a fact that these bulbs have been found in old homes in Hawaii, but they were also used in other states, like Florida for example, where merchant ships were often torpedoed by german submarines when their silhouettes could be seen against coastal city lights.
These bulbs were made by Wabash Appliance Corporation from Brooklyn, N.Y., however other manufacturers (like General Electric, Warren Lamp Company, Westinghouse, SAVE) also made their own versions. Here's a version by Westinghouse. Wabash chose radio tube glass envelopes for their bulbs, while G.E. chose the regular appliance bulb shape (A-17 shape). Yellow and Blue Blackout bulbs were also made by Wabash, the blue ones being the hardest to find (blue ones may have been the first made; see ad below). These bulbs are coated on the inside with a mirror-like silvery coating, which helps concentrate the light on the colored tip. Blackout bulbs were not the only "blackout" accessory produced; Plastic covers for essential lights such as car and bicycle headlights were also made, as well as black curtains for windows. Something worth noting about Wabash blackout bulbs is that the yellow bulbs are always labeled "Blackout Unit", while the Blue and Red ones are labeled "Blackout Bulb".
From The American Horologist and Jeweler magazine, February, 1942:
Silver-Lined Blackout Bulb Designed
Designed for blackout lighting in air raids, the new Wabash Blackout bulb just announced by the Wabash Appliance Corporation, Brooklyn, N. Y., provides downlighting in a soft beam of blue light that is safe for indoor visibility during blackouts. The bulb is lined inside with a pure silver reflector lining that hides all filament glare and projects the light down-ward. Light leaks are prevented by a black silicate coating that covers the bulb up to the extreme lighting end which is a deep blue. The new bulb consumes 25 watts and will list at 45c.
