Pierre Cartier established a New York City branch in 1909, moving in 1917 to 653 Fifth Avenue, the Neo-Renaissance mansion of Morton Freeman Plant (son of railroad tycoon Henry B. Plant), designed by architect C.P.H. Gilbert. Cartier purchased it from the Plants in exchange for $100 in cash and a double-stranded natural pearl necklace valued at the time at $1 million. By this time, Cartier had branches in London, New York and Saint Petersburg and was quickly becoming one of the most successful watch companies. Designed by Louis Cartier, the Tank watch was introduced in 1919 and was 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 its watches 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. Re-organization After the death of Pierre in 1964, Jean-Jacques Cartier (Jacques's son), Claude Cartier (Louis's son), and Marion Cartier Claudel (Pierre's daughter)—who respectively headed the Cartier affiliates in London, New York, and Paris—sold the businesses. In 1972, Robert Hocq, assisted by a group of investors led by Joseph Kanoui, bought Cartier Paris. In 1974 and 1976, respectively, the group repurchased Cartier London and Cartier New York, thus reconnecting Cartier worldwide. The new president of Cartier, Robert Hocq, coined the phrase "Les Must de Cartier" (a staff member is said to have said "Cartier, It's a must!" meaning something one simply must have) with Alain Dominique Perrin, who was a General Director of the company. As a result, in 1976, "Les Must de Cartier" became a diffusion line of Cartier, with Alain D. Perrin being its CEO. In 1979, the Cartier interests were combined, with Cartier Monde uniting and controlling Cartier Paris, London, and New York. Joseph Kanoui became vice president of Cartier Monde. In December 1979, following the accidental death of president Robert Hocq, Nathalie Hocq (daughter of Hocq) became president. Recent development In 1981, Alain Dominique Perrin was appointed Chairman of Cartier SAA and Cartier International. The next year, Micheline Kanoui, wife of Joseph Kanoui, became head