The Rolex Oyster Perpetual Datejust is a certified, self-winding chronometer wristwatch manufactured by Rolex. When it was launched in 1945, the Datejust was the first wristwatch with an automatically changing date function. The original Datejust model REF: 4467 was only available in 18 karat gold and had a small bubble back winder with a deeply domed back. It also featured a waterproof Oyster case, a fluted bezel, and a signature Jubilee bracelet, making it instantly identifiable as a Rolex. Rolex cyclops lens Closeup Look Over the years, the Datejust movement went through subtle improvements to its features while remaining true to its original design. Several years after its debut, In 1954, Rolex added the now famous “Cyclops Lens” as a major update. The Datejust is offered with two classic Rolex bracelets: the jubilee and the oyster. The original Datejust was launched with a case size of 36mm. Later, however, ladies' and mid-sized versions became available. The Turn-o-Graph model was introduced in 1955 as an award given to US Air Force pilots returning from combat missions. It featured a rotating bezel marked to 60 minutes, which can be used to measure time intervals. Datejusts of this type have been nicknamed "Thunderbirds". Chuck Yeager wore one of these models when he broke the sound barrier. This would be the basis for the Rolex Explorer (designed for Sir Edmund Hillary's Mount Everest expedition), the Rolex Submariner, and the Rolex Sea Dweller. In 2009, the Rolex Oyster Perpetual Datejust II was released. Its case is bigger than the standard Datejust and it also features an updated movement. The men's size is 41mm diameter and it is only available in steel with white, yellow or rose gold on an Oyster bracelet. In 2016, the Rolex Oyster Perpetual Datejust 41mm was released. The watch comes in two-tone stainless steel and 18k yellow or 18k everose gold (Rolex's version of rose gold). The 2016 41mm Datejust is on a jubilee bracelet. While the Datejust 41 has a similar-sized 41mm diameter case as the Datejust II, the Datejust 41 has smaller indexes and a thinner bezel compared to the Datejust II.