Rolex Explorer 5504 Gilt Chapter-Ring Tropical Underline DialThis reference 5504 was introduced in 1958, bridging the gap between a dress watch and a sports watch. It served as a more budget friendly alternative to the pricier Explorer 6610, as the 6610 was chronometer certified, whereas the 5504 used the new calibre 1530 movementmore compact yet still highly accurate. Because the movement was not chronometer certified, the dial is marked Super Precision instead of Chronometer. The 5504 shared its 36 mm case