This is the HP QDSP-6064 bubble display, a tiny, 4-digit, 7-segment numerical indicator. THis little guy is perfect if you need some user feedback from your system, but don’t want to fiddle with LCDs or other display options. The Bubble Display comes in an easy-to-use 12-pin DIP package and can be used in breadboards, protoboards, or PCBs.

These bubble displays have a peak forward current per segment of 5mA at a peak forward voltage of 2V. Thanks to a neat magnification technique used by the QDSP-6064 (giving it the "bubble" name), the luminosity is intensified making lower power consumption possible.