Modern time-reckoning in equal hours was not introduced into Japan until 1870. Before this time, Japan used a 'temporal hours' system similar to that of Europe's in the middle ages, the period of dawn to dusk being divided into six equal hours and the period of darknes also into six equal hours. A daylight hour was in general of different length from a night hour and both varied according to season. This clock's dial has the numeral's spaced differently for day and night. The dial rotates clockwise behind a fixed pointer and the hour marks are adjustable in a grooved ring in the dial. The clock is spring-driven and controlled by a short pendulum, the striking being released hourly by pins which project backwards from the hour marks.
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