Comparing to other sport watches of Rolex including Submariner, Daytona, GMT-Master and so on, Air-King is much cheaper. In fact, Air-King has a long history too.
You may think the Air-King has close relationship with planes. In fact, it is relative to the air war. Rolex launched a variety of sky-related watches which were all begun with Air, including Air Lion, Air Giant, Air King and Air Tiger in order to pay tribute to the British pilots who participated in the “British Air War” during World War II. Only the Air-King has been maintained to today. Looking at the picture, this model with gold case was the Air-Giant that had disappeared already.
In 1957, modern Air-King was created, becoming a big collection of sporty Rolex. The first model is ref.5500 which features a understated appearance including the silver dial and Oyster steel case. It determined some basic characteristics of modern Rolex Air-King, including polished bezel, simple dial and 34 mm case.