Normally associated with certain watches of the late 17th and early 18th centuries, though a few such dials were made for both longcase and bracket clocks. These were night clocks, the figures occurring as slits behind which the light from a lamp shines through to show the time. In this type of dial the hour appears in a disc which advances from left to right across a segmental slot marked along the edge in minutes and quarters. As one hour completes its journey along the slot the next hour appears on the left, marking the divisions of the following hour. There were two basic methods by which this action was achieved. In one, the hour discs were formed into a twelve-piece chain carried around a ten-sided wheel, bringing the correctly numbered disc into place at each succeeding hour. The other system employed a large revolving disc with two small revolving discs mounted on it opposite each other, one bearing the odd numbers I to XI and the other the even ones II to XII. Each smaller disc rotated one figure at each half-revolution of the main disc, bringing the respective hours into view as they moved along the aperture in the dial.