This clock by Salomon Coster (d. 1659) of The Hague is one of the earliest pendulum clocks ever made. The Dutch scientist Christiaan Huygens (1629-1693) made the first successful pendulum clock in December 1656 and in the following year he granted Coster the sole right to make them. In effect Huygens had used a pendulum to control a conventional spring-driven clock with a verge escapement by turning it on its side and coupling the oscillating action produced by the verge to the pendulum. This resulted in the pendulum swinging through a wide arc and Huygens was aware that the pendulum was not completely isochronous, i.e. the clock would run slightly slower as the arc increased. He proposed to overcome this defect by fitting cheeks at the pendulum suspension point which would progressively reduce the effective length of the pendulum as the arc increased. All these features are present in the Coster clock.