Rolex introduced the Explorer II series in 1971 to complement the Explorer line. It features an additional 24-hour hand like the GMT-Master but the bezel is fixed in place. This 24-hour indication, among other things, has been designed with regard to professional cavers, for whom a reliable temporal orientation independent of the outside world is of the utmost importance. Accordingly, at the design of the dial a special emphasis was put on excellent readability, even in the dark.
This original Explorer II Ref. 1655 used a 39 mm case, but was enlarged for Ref. 16550 and Ref. 16570 with a larger 40 mm case. This new version, introduced in 2011 at Baselworld to celebrate the 40th anniversary of the model, features an even-larger 42 mm case. In keeping with its sporting intent, it used an Oyster bracelet and featured crown guards. The bezel is marked with numerals at even numbers between 2 and 24 and triangle markers between. The dial is similar to the contemporary Submariner with a large triangle marker at 12 00, large bar markers at 6 00 and 9 00, and smaller dots at the other hours. There is a date window at 3 00 with a cyclops magnifier. The hands are Rolex “Mercedes” style, with the 24 hour hand using an arrow point.
Although the Submariner-style dial is similar to more recent Explorer II models, the new Ref. 216570 recalls the original Ref. 1655 with a large orange arrow pointer on the 24 hour hand. This feature was greatly missed since Ref. 1655 was retired in 1984. The hour and minute hands are widened to allow for better visibility and the lume is upgraded to Chromalight that glows bluish in the dark. The bracelet features the Oysterlock clasp which offers a 5 mm extension.
Like recent references, the 24 hour hand is independently adjustable, so the Explorer II can display a second timezone. This Ref. 216570 uses the new Cal. 3187 with the rugged and anti-magnetic Parachrom Blu hairspring.