Rolex's dedicated adventure watch, the Explorer, traces its origins back to mountain climbing in 1953. In 1971, however, another watch joined the collection with the name Explorer II and a quite different set of features, looks, size and purpose. Rather than for scaling peaks, the original Explorer II was intended for plumbing the depths of caves.
A 24-hour hand and bezel were meant to keep the likes of spelunkers or arctic explorers oriented when it might be easy to lose track of whether it's day or night. Although it looked like a GMT watch with its prominent, arrow-shaped fourth hand and the steel bezel, it functioned differently: Unlike, say, on the Rolex GMT Master, the bezel was fixed (non-rotating) and the 24-hour hand couldn't be set separately from the main time (though this changed in later versions).
There have been five Explorer II iterations to date. The very first reference looked and functioned a bit differently than the modern variation, but the Rolex Explorer II that's well known today was more or less established in 1985. The differences between the models have sometimes been subtle and other times significant, so here's a breakdown of how this iconic watch has evolved over the decades.
1971: Reference 1655
The first Explorer II established several of the key features that have shown continuity through the variations, but it's also the most distinct compared to later versions. The steel 24-hour bezel and brightly colored 24-hour hand have characterized the line, but the reference 1655 had a blocky hands and indices with a kind of military look that would later be replaced by more familiar Rolex design elements.
Bonus trivia: Though this model is sometimes called "the Steve McQueen," there's no known connection between this watch and the actor better known for wearing certain other watches.
Movement: Cal. 1575 automatic
1985: Reference 16550
Suddenly, in 1985, something much closer to the Rolex Explorer II we know today was born: Its size increased from 39mm to 40mm, it was outfitted with the unmistakably Rolex Mercedes hand set and dial, it received a sapphire crystal — and it got a new movement and a white-dial version. With changes big and small, this was a totally new watch in multiple ways.
The new movement made the 24-hour hand separately adjustable from the main time — meaning it could be set to display a second time zone (or used for the current time zone as originally intended, of course). That made it a true GMT watch, though the bezel remained fixed (as it still does). This helped differentiate it functionally from the GMT Master II within Rolex's lineup, and the white dial version did the same. The black and white ("Polar") dials have remained the available options to this day.
It's also notable that the bright orange 24-hour hand was toned down: now it only featured a red stem — but don't worry, the fully orange hand would come back in a later generation. A wider bezel further added to the watch's bolder size and presence.
Movement: Cal. 3085 automatic GMT
1989: Reference 16570
1989 saw the Explorer II get a new reference number and only very slight updates. It received a new movement, the cal. 3185, though later models of the same reference used the very similar cal. 3186. On the white dial "Polar Explorer," the hour markers were now outlined in starkly contrasting black rather than white gold as was the case previously — and the result is visually pretty striking.
The lume used on this reference was also updated over time — first it used tritium, followed by LumiNova and finally, Super-LumiNova.
Movement: Cal. 3185 automatic GMT; cal. 3186 automatic GMT
Lume: Tritium; LumiNova; Super-LumiNova
2011: Reference 216570
This is essentially the Rolex Explorer II we have today. Its case size now measured 42mm, and the all-orange 24-hour hand of the original 1971 model was back. It looks refined all around, but the increase in size was always going to be controversial. The dial was now illuminated with Rolex's own Chromalight material, providing a minty blue glow, and the watch's rehaut engraved with a repeating "ROLEX."
Movement: Cal. 3187 automatic GMT
2021: Reference 226570
For the watch's 50th birthday in 2021, the brand stuck to its winning formula and gave the current-generation Explorer II a new reference number and some general upgrades. The size, the functionality and the look are all more or less unchanged. What's new are the latest Rolex movement, the latest Rolex lume (an "optimized Chromalight display") and bracelet, and a marginally thinner case. Rolex changed only what it felt could be improved upon, because that's how the company rolls.
Movement: Cal. 3285 automatic GMT