This is the smallest incandescent bulb from my collection. I don't know if it is the smallest ever made.
It is a micro bulb used to back light the LCD display in a low budget wristwatch. The bulb measures 1/16 inch (1.5 mm) in diameter by 1/8 inch (3 mm) long. not including the wires. It dates to 1989. Watches from that era also used red 7 segment LED displays.
The lamp draws 12 milliamps current at 1.5 volts, which works out to 18 milliwatts.
I have grain of wheat bulbs, but this one is much smaller. Does anyone else have any bulbs like this or smaller?