Abstract: The back cover (51) of the watch case carries a middle-bezel and forms a plate. At its center there are superimposed and concentrically pivoted, respectively, a ratchet crown-wheel (1.6) inside which a mainspring is housed, driving a core (1.3) fast with an hour-disc (1.1) comprising a toothing on its periphery, and a transparent minute-disc (1.2) comprising also a toothing on its periphery. These discs mesh on the one hand with a drive train (2, 3, 4) by which the minute-disc is driven by the hour-disc and, on the other hand with a winding and time-setting mechanism both located outside of the discs and at least partially at the same height as these discs.