The clocks at Moscow’s Kievsky railway station have a unique ancient mechanism with a 120kg weight and lots of gears and components. They have been in operation since 1917.
Clock fixer Maksut Safin has worked with the mechanism for the last 3 years. He used to be a railway engineer, but when his predecessor retired he took over the job, though there’s no explicit instruction manual for this mechanism. He says it's no big deal, but maybe that's just false modesty.