Benoit Frigon wrote an article detailing his alarm clock running Linux project, that is available on github:
This is the display i made for my alarm clock project. The first version was a 24×7 LED matrix but later changed the design for a four digits seven segment display. I decided to keep the drawings for the LED matrix and named it model A and Model B for the segment display.
The display is encapsulated in clear casting epoxy and is 5 inches wide by 2 ¼ inches high by 1 inch thick.
More details at Benoit Frigon’s project page.