Designed by Louis Cartier, the Tank watch model was introduced in 1919 with a design inspired by the newly introduced tanks on the Western Front in World War I. In the early 1920s, Cartier formed a joint-stock company with Edward Jaeger (of Jaeger-LeCoultre) to produce movements solely for Cartier. Cartier continued to use movements from other makers: Vacheron Constantin, Audemars Piguet, Movado and LeCoultre. It was also during this period that Cartier began adding its own reference numbers to the watches it sold, usually by stamping a four-digit code on the underside of a lug. Jacques took charge of the London operations and eventually moved to the current address at New Bond Street.