The Aurore 390 watch movement is an open face calibre movement that was predominantly produced for a specific model featuring a 24-hour display during the period of 1941-1946. It incorporates a monometallic screw balance with four adjustment screws and utilizes an Elinvar Extra Breguet hairspring. Noteworthy features of this movement include a hack feature, allowing for precise time setting, as well as its stem wind and set functionality. Additionally, it boasts a sweep seconds hand, making it suitable for accurate timing purposes. The Aurore 390 movement is an American-made mechanical movement and was widely used by the military.