Tritium Under Steel: The 1995 Rolex Explorer II 16570 Black Dial

A 1995 Explorer II sits squarely inside the only stretch of the 16570's twenty two year run when the reference left Geneva with tritium on its dial. Black lacquer, applied markers in white gold surrounds, a Mercedes hour hand and a red 24 hour hand pointing at a steel bezel that will never turn: this is the Explorer II in its first form, built three years before Rolex abandoned radioactive lume for good. The watch it descends from was made for people working underground, where there was no sun to tell them the time of day, and nearly every detail on this 40mm case still traces back to that brief.

The Explorer Before the II

Rolex registered the Explorer name in January 1953, months before Edmund Hillary and Tenzing Norgay stood on the summit of Everest that May. A Rolex Oyster Perpetual chronometer, reference 6098, went up with that expedition, and Monochrome treats it as a pre-Explorer. The Explorer that followed settled into a simple formula: a black dial, luminous 3, 6 and 9 numerals, and nothing else to read at a glance. The reference 1016, which ran from 1963 to 1989, refined that formula for more than a quarter of a century and gave Rolex a watch defined by what it left out.

By the start of the 1970s, Rolex had a watch for mountaineers, one for divers in the Submariner, and one for pilots in the GMT-Master. What it did not have was a watch for people who had no sky at all.

1971: A Watch for the Dark

In 1971 Rolex introduced the reference 1655, the first Explorer II, aimed at speleologists. Monochrome describes it as a tool watch for cave exploration, and Beyond the Dial places it in the catalogue from 1971 to 1984. The problem it solved was specific. A caver spending days underground loses any sense of whether it is morning or evening, and a twelve hour dial cannot help, because four o'clock looks the same whether it is before dawn or late afternoon.

Rolex's answer was a second hour hand that turned once every twenty four hours, pointing at a fixed steel bezel engraved with a twenty four hour scale. On the 1655 that hand was locked to the main hour hand, so it could not be set to a second time zone. It answered one question: day or night. The bezel was fixed because there was nothing to adjust, and Beyond the Dial notes that the fixed steel bezel was unique to the Explorer II among Rolex sports watches of the period.

Black was the only colour

The 1655 was offered with a black dial only. The white Polar dial that many now associate with the Explorer II did not arrive until the following reference, which makes the black dial on a 16570 the continuation of the original rather than one option among two. When Rolex drew the Explorer II for the first time, it drew it in black.

1985: The Hour Hand Comes Free

The reference 16550 replaced the 1655 in 1985 and changed what the watch was for. Its calibre 3085 allowed the local hour hand to be set independently of the 24 hour hand, which turned a day and night indicator into a genuine second time zone. The case grew to 40mm, a sapphire crystal replaced acrylic, the dial gained Mercedes hands and applied markers, and the white Polar dial joined the black one.

The bezel stayed fixed. That is the quiet oddity at the centre of every Explorer II made since: once the 24 hour hand could track a second time zone, a rotating bezel would have allowed a third, as it did on the GMT-Master. Rolex kept the solid steel bezel anyway. The Explorer II remained visually a cave watch even after it became a traveller's watch, and that decision is what keeps it distinct from every other Rolex GMT.

1989: The Reference 16570

The 16570 arrived in 1989 and became the longest running Explorer II. Monochrome gives its production as 1989 to 2010, and Beyond the Dial extends it to 2011, when the 42mm reference 216570 took over. Across that span the external design barely moved: a 40mm Oyster case in stainless steel with crown guards, a screw down crown, a sapphire crystal and the fixed bezel with its twenty four hours engraved directly into the steel, even numbers written out and odd hours marked by hash lines.

Calibre 3185

The new reference brought a new movement. The calibre 3185 was introduced in 1989 with the GMT-Master II 16710, and CaliberCorner records it as built on the architecture of the calibre 3135. It runs at 28,800 vibrations per hour on 31 jewels, measures 28.5mm across and 6.45mm deep, winds automatically in both directions, stops its seconds hand when the crown is pulled for precise setting, and uses Rolex's Kif Elastor shock protection. The independent hour hand, which jumps in one hour steps, was developed in response to demand from professional aviators who needed to change local time quickly without stopping the watch.

The 3185 stayed in the 16570 until around 2005, when Rolex replaced it with the calibre 3186 and its Parachrom hairspring. A 1995 watch belongs firmly to the 3185 years.

Two time zones on a bezel that does not move

Using the 16570 as Rolex intended is simple once the logic is clear. The 24 hour hand is set to home time and left alone. When the wearer lands somewhere new, the crown is pulled to its first position and the local hour hand is jumped forward or back in one hour steps until it shows local time, while the minutes, seconds and 24 hour hand carry on undisturbed. The bezel then reads home time against the red hand, and because it counts all twenty four hours, it also shows at a glance whether home is in daylight or darkness. The day and night question the 1655 was built to answer is still being answered, now for a city on the other side of the world rather than the surface above a cave.

The same calibre powered the GMT-Master II 16710 through the same years, so in 1995 the two watches shared a movement and a function while looking nothing alike. The GMT-Master II wore a rotating bezel with a coloured insert and could track a third zone. The Explorer II wore bare steel and tracked two. It is the clearest case in the Rolex catalogue of the same mechanism being given two different characters by what surrounds it.

The Black Dial in the Tritium Years

Beyond the Dial divides the 16570 into four generations, and the first, from 1989 to 1997, is defined by its luminous material. These dials carry tritium, and the line printed at six o'clock reads SWISS, followed by T < 25.

What T < 25 means

Tritium is a radioactive isotope of hydrogen that makes luminous paint glow continuously without first being charged by light. Rolex used it from the 1960s, when it replaced radium, until 1998, when the company moved to Luminova and soon after to Super-LumiNova. The T < 25 marking was a regulatory declaration that the dial contained less than 25 millicuries of tritium. It was a label for customs and safety authorities, not a design flourish, and its presence on a dial is the clearest indication of when that dial was made.

Tritium has a half life of about twelve and a third years, so its glow fades steadily from the day it is applied, and the luminous compound tends to warm in tone over the decades. A dial printed in 1995 has passed through more than two of those half lives. The material on a first generation 16570 is doing exactly what the chemistry says it should, and the way it ages is part of the reason this generation reads differently from the later Super-LumiNova watches.

White gold, black lacquer and a red hand

On the black dial, the hour markers are applied and set in white gold surrounds, so the luminous plots sit within polished metal frames that catch light even when the lume is not visible. The hour and minute hands are white gold as well, with the Mercedes emblem on the hour hand that Rolex uses across its professional watches. The 24 hour hand is red on this generation. The 1655 had carried an orange arrow, and Monochrome notes that the orange hand only made its return on the 216570 in 2011. Against black lacquer the red hand and the steel bezel are the two elements the eye finds first, which is the right order for a watch whose purpose is reading that second hour.

What 1995 Means on This Watch

Rolex adopted letter prefix serials in 1987, and a watch from 1995 carries an S or W prefix, the two letters that overlap across that year, engraved between the lugs at six o'clock. A 1995 16570 sits in the middle of the tritium generation, six years after the reference was introduced and three years before Rolex dropped radioactive lume across its entire range.

Everything about the case matches its period. It has drilled lug holes, which Rolex retained on the 16570 until around 2002. According to Beyond the Dial, first generation watches were delivered on the Oyster bracelet reference 78360 with hollow 501B end links and a pressure clasp, before the second generation moved to the 78790 with a locking clasp. The bracelet, like the dial text, is part of how the reference records its own timeline.

The year also places the watch in context beyond Rolex. In 1995 the 16570 was the only Explorer II in the catalogue, sold alongside the 36mm Explorer 14270 that had replaced the 1016 in 1989. The two watches shared a name and a heritage but very little else. One was the purest expression of the 1953 idea, and the other carried the cave explorer's bezel and a traveller's hour hand into a 40mm steel case that would change remarkably little over the next sixteen years.

Final Thoughts

What we love about this 1995 Explorer II is how directly it carries its own history. The fixed steel bezel is there because speleologists in 1971 needed to know whether it was day or night. The black dial is there because that was the only colour the first Explorer II ever wore. The independent hour hand arrived in 1985 and turned a cave watch into a traveller's watch without anyone changing its face, and the calibre 3185 made that hand fast and precise. The tritium generation is the Explorer II before Rolex settled on the modern luminous materials it still uses, and a 1995 watch sits right in the middle of it. Thirty one years on, it is still a watch for knowing whether it is light or dark somewhere else, drawn in the colour the first Explorer II was drawn in.

References

1. Monochrome Watches, In-Depth: The History of the Rolex Explorer II: https://monochrome-watches.com/history-rolex-explorer-ii-adventure-watch-gmt-1655-16550-16570-216570-226570-in-depth/

2. Beyond the Dial, Collector Guide: The Rolex Explorer II, All References In Detail: https://www.beyondthedial.com/post/collector-guide-the-rolex-explorer-ii-all-references-in-detail/

3. Monochrome Watches, In-Depth: The History of the Rolex Explorer: https://monochrome-watches.com/history-rolex-explorer-from-1953-36mm-1016-14270-114270-214270-124270-in-depth-review/

4. CaliberCorner, Rolex Caliber 3185 Watch Movement: https://calibercorner.com/rolex-caliber-3185/

5. Everest Bands, Comparing Every Rolex Lume: https://www.everestbands.com/blogs/bezel-barrel/comparing-every-rolex-lume

6. Millenary Watches, What is a Rolex Swiss Only Dial?: https://millenarywatches.com/rolex-swiss-only-dial/

7. Wikipedia, Tritium: https://en.wikipedia.org/wiki/Tritium

8. Own The Watch, The Rolex Explorer II Ref. 16570: https://www.ownthewatch.com/p/rolex-explorerii-16570

9. SwissWatchExpo, Rolex Serial Numbers: https://www.swisswatchexpo.com/rolex-serial-numbers/

10. Diamond Banc, Rolex Serial Numbers: What You Need to Know: https://www.diamondbanc.com/sell-jewelry/watches/rolex/rolex-serial-numbers-what-you-need-to-know/

• The case remains in excellent condition 
• Very little wear
• Bracelet excellent

• Dial & hands very good
• Light Cream patina