“The Berlin Clock, BerlinUhr or Mengenlehreuhr, was probably the very first digital clock. It has been there since 1975… Lots of info you can find here: https://en.wikipedia.org/wiki/Mengenlehreuhr How is it made, how do you tell the time? In short, there are fous rows of lights. The upper row gives the hours x 5, the next the “single hours” from 1 to 4. The third row gives us the “minutes x5”, the bottom row the minutes.”