1958 Rolex Super Precision Explorer (Ref. 5504) Gilt Chapter Ring

In 1957, Rolex released the stainless steel Air-King ref. 5500 with a 34mm case and time-only functionality that same year Rolex introduced the ref 5504 which instead of leveraging a 34mm case used a larger 36mm case and was similar in design and feel to the Rolex ref 6610 explorer 1 references.  It's been said that the 5504 was a more economical version of the 6610 Explorer 1 as the 5504 is a  “SUPER PRECISION” leverages the Rolex caliber 1530 movement which is a non-chronometer rated movement and was offered through the British NAAFI (the British version of the military PX). 

The Rolex Explorer I references bridge the gap between a dress watch and a sports watch. Without the crown guards and rotating bezels commonly found on sports models offered by Rolex, the Explorer I has a cleaner, sleeker profile while incorporating recognizable sport model features into the dial. The highly visible block indices, luminescent numerals at the 3 o'clock, 6 o'clock, and 9 o'clock positions, and Submariner style triangle at the 12 o'clock position allow for readability under any conditions. The Submariner hands featured on the Ref. 5504 add to the unique feel and appearance.