From the 1930s, Rolex began to equip numerous expeditions with Oyster Perpetual watches. The feedback received was used to develop what became known as the Professional category: watches that serve as tools, such as the Explorer and Explorer II. Rolex watches have taken part in some of humanity’s greatest adventures. One such occasion was the 1953 expedition to Everest, led by Sir John Hunt, on which Sir Edmund Hillary and Tenzing Norgay Sherpa become the first to summit the world’s highest mountain.