https://www.bobswatches.com/rolex-blog/buying-guides/rolex-5500-review-ultimate-guide.html

it is an absolutely fascinating piece of Rolex’s history and serves as proof that sometimes things don’t always make as much sense as they should when it comes to vintage watches. So, today we take a closer look at both versions of the Rolex reference 5500 with detailed reviews of the Air King ref. 5500 and the Explorer ref. 5500 to provide some insight on this somewhat mysterious vintage Rolex reference.