This is the entry level Rolex model addressed to people who are inclined to spend a “fortune” on a watch. This watch has an unprecedented historical value in the Rolex Oyster Perpetual range since it was used by British aviators in WWII. Apparently the Air-King was the watch of choice for battle of Britain fighter pilots and Hans Wilsdorf, the founder of Rolex was so moved by the brave British pilots that decided to honour them with a new line of manual wind Oysters.

While the Oyster Royal line existed already before the war Rolex began producing larger watches coding them with names like “Air Tiger,” “Air Lion,” “Air Giant,” and “Air King.”
What was then considered a large dial – 32 to 33 mm diameter – is now small in comparison, as most Rolex sports models feature a 40 mm or larger dials.
The Air line of watches remained in production until the early 1960s. In the end only the Air-King survived and was eventually fitted with an automatic movement.The Air-King is not as fancy or as over-engineered as some other Rolex watches yet it is an elegant watch and most importantly has a great history behind it. I believe that it is one of the most overlooked watches out of the Oyster Perpetual range although it deserves more attention by prospective buyers. Today the current Air-King model range even comes with COSC certification. They have also recently been redesigned with new dials and bracelets.
I am sure more educated members than myself on the subject will contribute some more information as well as photos on this thread.   

Technical data
Certification: Chronometer
Size: 34 mm
Bracelet: Oyster featuring Oysterclasp (with easy link on new models)
Movement: Self-winding cal. 3130
Water-Resistance: Waterproof to 100 metres/330 feet
Crystal: Sapphire