Do you know what the crystals do? One of them undoubtedly provides a timebase for the clock function, and what the other(s) might do is clearly a mystery.

If you map out the anodes and cathodes in the LED display, perhaps you'll see a pattern that makes some of the circuitry understandable. Figuring out what the transistors do might be of help, too. It might be helpful to draw a schematic for your own use. Pay particular attention to resistors and their relative position with respect to supply and ground connections.

RE