DIAM. 55 mm. This very high quality and unusual watch has provision for displaying the time in two different zones on both a 12-hour and 24-hour basis. Each dial is independently adjustable so that both local time and standard time can be set. For the 24-hour dial, the hour hand makes one full revolution in 24-hours, the minute hand one revolution per hour. The 12-hour dial operating in the usual way. Remarkably the hands for all functions are driven from the center. The constant running center-seconds has a split-seconds function that can be used as a chronograph but without the return-to-zero function of a true chronograph. The adoption of universal time zones had not yet taken place when this watch was made although Greenwich meantime was officially in place as standard time by 1880. Before the adoption of time zones, people used local solar time (originally apparent solar time, as with a sundial; and, later, mean solar time). Mean solar time is the average over a year of apparent solar time. Its difference from apparent solar time is the equation of time This became increasingly awkward as railways and telecommunications improved, because clocks differed between places by an amount corresponding to the difference in their geographical longitude, which was usually not a convenient number. This problem could be solved by synchronizing the clocks in all localities, but then in many places the local time would differ markedly from the solar time to which people are accustomed. Time zones were first proposed for the entire world by Canada's Sir Sandford Fleming in 1876 as an appendage to the single 24-hour clock he proposed for the entire world (located at the center of the Earth and not linked to any surface meridian). In 1879 he specified that his universal day would begin at the anti-meridian of Greenwich (now called 180°), while conceding that hourly time zones might have some limited local use. He continued to advocate his system at subsequent international conferences. In October 1884, the International Meridian Conference did not adopt his time zones because they were not within its purview. The conference did adopt a universal day of 24 hours beginning at Greenwich midnight, but specified that it "shall not interfere with the use of local or standard time where desirable". Nevertheless, most major countries had adopted hourly time zones by 1929. Today, all nations use standard time zones for secular purposes, but they do not all apply the concept as originally conceived. Newfoundland, India, Iran, Afghanistan, Burma, the Marquesas, as well as parts of Australia, use half-hour deviations from standard time, and some nations, such as Nepal and the Chatham Islands use quarter-hour deviations. Greenwich Meantime (GMT) Was established in 1675, when the Royal Observatory was built, as an aid to determine longitude at sea by mariners. The first time zone in the world was established by British Railways on December 1, 1847 - with GMT hand-carried chronometers. About August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory, Greenwich. Even though 98% of Great Britain's public clocks were using GMT by 1855, it was not made Britain's legal time until August 2, 1880. Some old clocks from this period (as with the present watch) have two dials or two sets of hands - one for the local time, one for GMT.