In the first episode, "Beyond the sky" in the bedroom scene, after the talk about waking up in a field in France, note the clock. He can't sleep, and all you can hear is the "tick-tock" of the clocks of the era... But, when he checks the time (3am, just so you know) look CLOSELY at the second hand...

The second hand on wind-up clocks have a staggered motion. Electric clocks are one fluid movement, as is shown..