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 in times known as "blackouts", in which there was reason to believe there was danger of an airstrike. When this happened, all normal bulbs were turned off, and these bulbs were used instead. The idea behind this probably was to make it difficult for enemy airplanes to accurately locate cities to attack. I heard a story about these bulbs from an eBay seller, he said that if patrolling troops saw light coming from your home during a "blackout", they could shoot out the source. (I haven't verified this, but it wouldn't surprise me if it's true). 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.
These bulbs were made by Wabash Appliance Corp. from Brooklyn, N.Y., however other manufacturers like General Electric also made their own versions. I've also spotted a version
made 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. 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 car and bicycle headlights were also made. An interesting detail about Wabash blackout bulbs is that their yellow bulbs are always labeled "Blackout Unit", while the Blue and Red ones are labeled "Blackout Bulb".