The Illinois 439 watch movement is a mechanical open face calibre with a Breguet hairspring, providing precise timekeeping. It is equipped with a stem mechanism without a setting-lever spring, ensuring smooth winding and easy time setting. The movement possesses the following functions: stem winding and setting, allowing for convenience in daily use, and a sub-second function for accurate timekeeping. The Illinois 439 movement was specifically designed for use starting from 1939.