Salomon Coster
Salomon Coster (c. 1620–1659) was a Dutch clockmaker of the Hague, who in 1657 was the first to make a pendulum clock, which had been invented by Christiaan Huygens (1629-1695). Coster's earliest pendulum clocks were signed "Samuel Coster Haghe met privilege", indicating that he had been authorized by the inventor to make such clocks. John Fromanteel, the son of a London clockmaker, Ahasuerus, went to work for Coster. He was one of many foreign clockmakers to soon make pendulum clocks following the prototype by Huygens and Coster. A contract was signed on 3 September 1657 between  Salomon Coster and John Fromanteel which allowed Fromanteel to continue making the clocks. This clock design was heralded as a new beginning in the clockmaking industry, due to its level of timekeeping accuracy which was previously unheard of. The oldest extant pendulum clock is signed by Salomon Coster and dated 1657. It is on display at the Boerhaave Museum in Leiden, the Netherlands. Coster died a sudden death in 1659.