This reminds me of an old Bosch clock I own. This was one of the early electric consumer clocks. It looks very futuristic. But inside, it is simply a mechanical clock with an electric motor attached to the wind-up mechanism. Every few minutes, the motor spins up for a second and winds the clock up again.

https://www.youtube.com/watch?app=desktop&v=0DU0KX9gIk8

The clock is extremely reliable, though. The last batteries lasted for 10 (!) years.