A simple, reliable system is a mainspring wound by a crank or by natural motion, with a basic verge or lever escapement. Wrap the spring around a sturdy metal rod, let the ratchet turn it whenever you shake the device or walk with it. The escapement releases the spring in tiny, steady ticks. If you can afford a tiny solar cell, feed it into a capacitor that charges the mainspring or a small battery that drives a tiny weight‑driven escapement. No batteries, no plastic. Just a good spring, a clean escapement, and a steady source of motion. Keep the gears clean and the escapement free of dust, and you’ll have a timekeeper that outlasts the digital lies.