 In 1903, Paris-based watchmaker to the French Navy, Edmond Jaeger, challenged Swiss manufacturers to develop and produce the ultra-thin movements that he had invented.Jacques-David LeCoultre, Antoine's grandson who was responsible for production at LeCoultre & Cie., accepted the challenge, giving rise to a collection of ultra-thin pocket watches, including the thinnest in the world in 1907, equipped with the LeCoultre Calibre 145.The same year, French jeweller Cartier, one of Jaeger's clients, signed a contract with the Parisian watchmaker under which all Jaeger movements for a period of fifteen years would be exclusive to Cartier.