This device is considered to be the first of it's kind, a 7-segment display made from LEDs. While this type of display had been around before, previous incarnations used neon lit segments (NIXIE) or Incandescent (Numitron) filaments to display numbers. This allowed digital displays to be driven directly from logic circuitry, without the need for voltage translators or other drive circuitry. These are original production MAN-1, and are evidenced by the M printed on top, and the clear case, the latter being replaced by a red lens in later production to hide the internal circuitry. Monsanto did license out the technology to other manufacturers, but these are made by the parent corporation and were originally sold to the Bell System for use in telephone switching products. Here's a page showing the devices lit. They're not really that bright.