In the modern culture, wrist watches have become symbols of status and style, rather than merely instruments to tell time. Today, many men wear wristwatches, especially prominent and wealthy men, who sport designer brands such as Rolex and Patek Phillipe. A long time ago, however, wristwatches were not generally worn by men, for most men preferred pocket watches, and would not desire to be seen wearing wristwatches. Women wore wrist watches much more than men, and even they did not truly appreciate it as much as society does today. The history of the wristwatch took a turn when soldiers began wearing them during combat. Pocket watches made it difficult for soldiers to operate efficiently, and wrist watches provided more ease and comfort. The invention of the wrist watch aided the British troops in their battle in the Anglo-Boer War in South Africa. With the help of the wrist watches, the British troops were able to synchronize their attacks and fight efficiently and successfully win. In 1906, the expandable flexible bracelet was invented, along with wire loops on watches. The glass crystal cases of the watches were very vulnerable to breaking during combat, so a new cover was invented to solve the problem. Pierced metal covers made out of silver were formed and positioned over the dial of the watch, thereby protecting the glass from breaking. During the time of the First World War, demand grew from soldiers over wrist watches, and the wrist watch became a popular item on the market. Hans Wilsdorf stood as a very important person that allowed for the progress of the wrist watch. Known as the founder of Rolex, he was very adamant in continually testing the wrist watches. He was even known as the first one to send wristwatches to be tested for accuracy in the Neuchatel Observatory in Switzerland. When soldiers returned from war sporting trench watches, the wrist watch lost its reputation as a feminine accessory, and men began wearing it as well. By the end of the war, transformations to the cases of the watches were introduced by designers such as Francis Baumgartner, Dennison and Borgel, who invented cases that were more durable as well as resistant to particles and water. In 1910, Rolex received the first wristwatch Chronometer awards in Bienne from the School of Horology. Four years later, Rolex received the Class A Certificate of Precision. In 1926, Rolex invented the first waterproof watch, named the Oyster. The wrist watch underwent many transformations; as new models were being introduced, many of the features of the wrist watch changed as well. The porcelain dials were replaced with new metal dials, which were stronger and more durable. Also, synthetic plastic replaced the glass crystals, which were very fragile and breakable. With the invention of the Auto Rotor by Rolex, self-winding watches were introduced. Wrist watches were not only stylish, but very useful for professional use. Rolex helped establish this reputation by introducing models such as the Submariner, Explorer, GMT-Master, Turn-O-Graph, and Milgauss.