Since its premiere in 1971, the Explorer II has only received four updates. The original ref. 1655 sets itself apart from later models mainly in its dial and bezel design. It has printed line indices on the dial, and the bezel's numerals are markedly thinner than those found on subsequent models. What's more, the numerals on earlier timepieces are separated by triangles, which have been replaced by lines on more recent models. This watch also features narrow baton hands instead of the Mercedes hands that are so common today. Furthermore, its luminous orange 24-hour hand ends in a large, arrow-shaped tip. The indices and other hands also glow in the dark thanks to a coating of radium-based material. Another notable difference is that the 1655 is only available with a black dial, while later versions also come in a white edition. Inside the 39-mm stainless steel case, you'll find the caliber 1575.
The next Explorer II followed in 1985 and brought with it numerous significant changes, especially to the dial. Listed under the reference number 16550, this model bears a stronger resemblance to the GMT-Master. For example, the original's stamped line indices gave way to round hour markers in white gold. The bar indices at 6 and 9 and triangle at 12 o'clock are also made of white gold. A tritium-based luminous material fills each index, guaranteeing optimal readability in the dark. Sapphire crystal, Mercedes hands, and a red 24-hour hand with a thinner arrow tip were also new to this timepiece. Furthermore, it was the first Explorer II to come with the option of a black or white dial. The caliber 3085 ticks away in both Explorer II and GMT-Master watches from this time period, meaning both watches can display the time in a second time zone.
The Explorer II Since 1989
The ref. 16570 debuted in 1989 and is nearly identical to its predecessors bar a few cosmetic changes. For example, models with white dials feature indices trimmed in black as well as black hands. The caliber 3185 powered these watches until 2007, after which it was replaced by the 3186. You can recognize later models by their lugs, which were no longer drilled through, and by the Rolex engraving on the dial's edge.
The Explorer II experienced its biggest update with the introduction of the ref. 216570 in 2011. Its stainless steel case is 42 mm in diameter and feels significantly heftier. This model was given a maxi dial with enlarged glow-in-the-dark indices and marked a return to the orange, arrow-shaped 24-hour hand found on the original Explorer II.
Its movement also received an overhaul. The caliber 3187 ticks away inside this timepiece. This automatic movement oscillates at 28,800 vibrations per hour (4 Hz) and has a 48-hour power reserve. It is incredibly precise and deviates from the reference time by a maximum of +/- 2 seconds per day. What's more, the 3187 features a blue Parachrom hairspring. This innovation is made of an anti-magnetic niobium-zirconium alloy and is ten times more resistant to shocks than conventional hairsprings. Rolex also equips this movement with their proprietary Paraflex shock protection system for added protection against hard jolts and other extreme conditions.
