Alfred Davis and his brother-in-law Hans Wilsdorf founded Wilsdorf and Davis in London, England in 1905. At the time they were importing Hermann Aegler's Swiss movements to England and installing them into cases made by Dennison. Originally jewelers were purchasing these timepieces and putting their own private label dials on them and the case was marked "W & D". By 1908, Wilsdorf registered the trademark "Rolex" and they opened an office in La Chaux-de-Fonds, Switzerland. By November 1915, the company changed its name to Rolex Watch Co. Ltd and in 1919 Hans moved the company from England to Geneva, Switzerland to avoid the post war taxes. In 1920 the company's name was changed to Montres Rolex S.A. and later to Rolex S.A. Development in timepieces became the focus as the company moved forwarrd and in 1926 Rolex developed and produced a waterproof and dustproof wristwatch. To help prove their skill and technical abilities they submerged these 'Oyster' models in aquariums. Rolex continued the push forward and in 1931, Rolex patented a self-winding mechanism called a Perpetual rotor, which became the basis of all future automatic watches.