In p>1931, Rolex made the "PERPETUAL" watch which became all the rage, bringing a revolution to the watch industry. This automatic watch has a pendulum thallium in the central axis, which can convert the slight movement of wrist swing into the power of the watch, so there is no need for manual winding. This was recognized as the most accurate and reliable automatic winding technology of watches at that time. In 1945, Rolex introduced the world's first watch that can automatically change the date. In 1956, it introduced a calendar with day display function, and there were 26 languages to choose from. Rolex watches have always been known for their professional functions, so they have won the admiration of professionals all over the world. In 1955, Rolex invented the pilot's watch so that people could measure the exact time in different time zones. In the same year, the diving watch developed by Rolex for deep-sea divers came out, and its waterproof depth reached 1 meters. The original logo of Rolex watch is a palm with five fingers extended, which means that the watch of this brand is completely crafted by hand. Later, it gradually evolved into a registered trademark of Crown to show its dominance in the field of watches. In the international market, the price of an ordinary Rolex watch ranges from $1, to $15,, which is not only due to the excellent quality of Rolex, but also because of its unique investment value. At an auction held in Geneva in 22, a 1952 Rolex perpetual calendar gold watch worn by the last Vietnamese emperor Baoda was sold at a sky-high price of 342, Swiss francs (then about 235,4 US dollars).