Time Keeper Forum
Having owned the Rolex Explorer II 216570 since early October 2011, it's about time that I make a review of it...
The various parts / aspects of the watch will get scores... here's the system:

  = Excellent 

 = Very Good

 = Good

 = Average

 = Bad

 = Terrible
The review will be divided into the following chapters:
- History Of The Rolex Explorer II
 
- Case
 
- Bracelet
 
- Crystal
 
- Dial And Legibility
 
- Movement
 
- Accuracy
 
- Summary
 
1. HISTORY OF THE EXPLORER II
In 1971, Rolex released the Explorer II ref. 1655. This tool watch 
featured a 24hour hand, fixed engraved bezel with 24hour graduation and 
was only availible with a black dial, and only in steel. The 24hour hand
 always stayed syncronised to the time the watch was telling... in other
 words, the Explorer II 1655 was not a "GMT" watch since you could not 
adjust the 24hour hand 
independently of the hour hand.
Rather, the 24hour hand - combined with the 24hour graduated bezel - was
 used to tell the wearer of the watch whether the hour hand is referring
 to for instance 10 o' clock AM or 10 o'clock PM; particularly useful to
 speleologists (cave explorers) who spent a lot of their work in dark 
caves, resulting in the cave explorers losing any notion of whether it 
was day or night outside the cave.
The dial and hands design of the 38mm diameter and 13.5mm thick Rolex 
Explorer II 1655 was quite unique; initially at its release featuring a 
straight seconds hand and a a big orange 24hour hand. Due to the rather 
big and bold 24hour hand, the Explorer II 1655 was nicknamed "Freccione"
 (meaning "Arrow") by Italian collectors.
The design of the hour and minute hand was unique, too, with a matte 
part around the hands stack, making the hands appear to "float" on the 
dial... no other Rolex watch used or has been using them since in quite 
this form, although Rolex besides the big orange 24hour hand made a 
historical nod to those "phantom" hands in 2011 with the release of the 
Explorer II 216570 (black dial). The Explorer II 1655 also featured 
small square hour markers corresponding to the uneven numbers on the 
fixed bezel.
According to an 
article by Mr M. Siegel, around year 1974 / 1975, the Explorer II 1655 received to updates:
- The straight seconds hand got a luminous dot near the tip (1974)
 
- The colour of the 24hour hand was changed from orange to red (1975)
 
Mr M. Siegel also claims that the Explorer II remained in that form ("2" above) until it was discontinued in 1985.
However, more recent studies done by collectors result in the consensus that the "Red 1655 Arrow Hand" actually never existed...
Rather, for a very brief period circa 1978 the 24hr hand was a different
 deeper shade of orange but was quickly changed back to the standard 
colour and stayed that way up until the Explorer II 1655 was 
discontinued.
Most people assume the hand changed colour in 1975 because the 1655 
brochure/booklet at that time showed a "redder" hand in the picture. 
This was a printing problem only.
 
Over the past 40yrs the orange hands have been very prone to fading - 
some way more than others depending on exposure to the sun.
 
Here are the two versions of the Explorer II 1655:
First version (1971 - 1974). Straight seconds hand:

(
Source)
Second version (1974 - 1985). Seconds hand with luminous dot:

(
Source)
In 1985, the Rolex Explorer II 16550 was launched. Although still being 
40mm in diameter, this Rolex was radically different from the 
predecessor model in as much as the 24hour hand was now de-coupled from 
hour hand, making the wearer of the watch able to move the 24hour hand 
back and forth in 1hour intervals, independent of the hour hand. In 
other words, the Explorer II 16550 could now be used as a "GMT" watch 
(although only able to track two time zones at a time).
Furthermore,  the design of the dial and hands was changed, leaving almost no resemblance to the Explorer II 1655. 
The Explorer II 16550 now had the Rolex typical skeleton (also known as 
"Mercedes") hands and a red GMT hand with a smaller, red triangle. There
 was also an option for either a white or black dial. The satinised 
bezel featured rather big and bold, fairly deeply engraved numbers.
Originally, the white dial Explorer II 16550 had unpainted dot hour 
markers... most likely made of white gold because Rolex switched from 
using steel hands and markers around that time.
Later, the dots indices on the white dial version were painted black. 
Interestingly, some of the early 16550's had a fault in the paint 
mixture, making the white dial become cream with time (also known as the
 "Cream Dial" Explorer II). Furthermore, the dial existed in a "Rail 
Dial" version (both on black and white dials) where one you draw an 
imaginary vertical line between the "Superlative" / "Officially" and 
"Chronometer" / "Certified". The black dial version sometimes developed a
 "Spider Web" effect due to a fault in the paint mixture:
"Cream and Rail Dial" Explorer II 16550:

(
Source)
"Spider Web" and "Rail Dial" Explorer II 16550:

(
Source)
The Explorer II 16550 was to be manufacture for only 3 years: 
In 1985 it received another update: The movement was changed from Cal. 
3085 to Cal. 3185, and the model reference number was hence changed to 
16570.
Still availible with either a black or white dial, the white dial now 
had black hour dots right from the start. Furthermore, the numbers on 
the fixed bezel were now less bold and deeply engraved:
Apart from the M-series and onwards where it received the Cal. 3186 with
 the inhouse made Parachrom Bleu hairspring, the Explorer II 16570 
continued virtually unchanged until 2011 when the Explorer II 216750 was
 released; 
one year later than expected / rumoured.
Now let's take a closer look at the Rolex Explorer II 216570:
2. CASE
One of the most striking details of the Explorer II 216570 is its bigger
 42mm case. It certainly has "wrist presence" on my 7½" wrist, almost 
filling my wrist out in width:
The lug style has been changed compared to the broad "block" lugs of the
 Rolex GMT II 11671x and Submariner Date 11661x, now more resembling the
 old-style lugs that had more taper to them. Additionally, like on the 
new GMT II and Submariner Date, the satination on the lugs is vertical 
and finer compared to the angled and coarser satination of the 5-digit 
Rolex sports models:
In my opinion, like on the Rolex Deepsea Sea-Dweller, also on the 
Explorer II 216750 Rolex managed to make the larger case look more 
proportioned due to those tapering lugs.
Furthermore, there is slightly more curve to the lugs and case when seen
 from the side as compared to the GMT II 11671x and Submariner Date 
11661x:
The bezel design has been changed a bit again. Still being satinised, 
the numbers on the bezel have become a bit bolder again, making the 
style resemble the Explorer II 16550 bezel font if one should compare it
 to earlier models. Like on the earlier models, the edge of the bezel is
 high-polished, making for a very attractive and elegant contrast to the
 satinised bezel:
The winding crown has been updated, too, now not more being a standard 
6mm Twinlock crown but a larger, 7mm Twinlock, like also seen on the 
Rolex Milgauss 116400. Compare with the Explorer II 16570:
Although I would have preferred a Triplock winding crown on the Explorer
 II 216570 like on the GMT II 11671x models, in my opinion the larger 
Twinlock crown still looks good on the watch.
The caseback sits fairly low, in fact making the watch not much thicker than the Explorer II 16570.
Here are the case dimensions, measured with a digital caliper gauge:
- Bezel edge to bezel edge: 41.5mm
 
- Case diameter incl. crown: 45mm
 
- Case Length: 48.7mm (lugs at 6 to lugs at 12)
 
- Case thickness: 12.40mm incl. caseback and crystal
 
- Lug width: 21mm (tapers down to the last link before clasp which is 15mm)
 
- Clasp length: 35mm (including the the small protution at the springloaded tip: 36mm)
 
- Crown  diameter: 7mm - same size as Milgauss 116400 crown (standard TwinLock is 6mm)
 
- Crystal diameter: 33.5mm*)
 
- Dial diameter: 30mm (from INNER edge of rehaut to the other)
 
- Width of minute hand: 2mm
 
- Width of indices: 2mm
 
- Weight incl. all links: 157g (same weight as Milgauss 116400)
 
*) Compare: crystal diameter of Rolex Explorer II 16570 which is 30.4mm:
Overall, I find the execution of the Explorer II 216570 case very elegant and stylish. It therefore gets:
SCORE: 
3. BRACELET
As expected like with the other updated Rolex watches, the Explorer II 
216570 got a new bracelet (Ref. 77210) with solid centre links and solid
 clasp, featuring the Easy Link that allows for 5mm instant expansion of
 the bracelet when engaged. The lugwidth is 21mm and suits the 42mm case
 diameter to perfection. The tapering lugs add to the wellproportioned 
case/band ratio:
The clasp is machined from one solid piece of 904L steel (same steel 
type used for the rest of the watch) and sits nicely centered on my 
wrist:
Unlike on the Explorer II 16550 and 16570, the Rolex coronet on the clasp now sits on the Oysterlock:
With all links installed and with the Easy Link folded in, the Explorer 
II 216570 sits extremely comfortably on my wrist. I believe the 
low-lying caseback adds to this comfort. 
From the manufacture, the bracelet ref. 77210 has the following link setup:
- 5 links on the 6 o'clock side (2 with screws) and 7 
links on the 12 o'clock side (4 with screws). Easy Link is not included 
in the count.
 
Overall, I cannot but give the bracelet the following score:
SCORE: 
4. CRYSTAL
I was pleased to see a bigger crystal on the Explorer II 216570! 
Like on the on the updated Rolex GMT II 11671x and Submariner Date 
11661x, it has an anti-reflective coated cyclops over the date aparture 
but (apart from its diameter), the crystal is different from the other 
updated Rolex watches mentioned in as much as the crystal sits higher. I
 have tried to capture it in this picture:
The higher standing crystal makes the new Explorer II slightly thicker 
than its predecessor model but also makes it look more "old 
fashioned"... a look which I like.
SCORE: 
5. DIAL AND LEGIBILITY
Like the Explorer II 16550 and 16570, the new Explorer II 216570 comes 
with a choice of either a white or a black dial. I chose the white dial 
since I find it easier to tell the time from and because I simply prefer
 the white dial on the Explorer II which also is a nice change to the 
black dial of my Daytona 116520.
Another reason as to why I opted for the white dial Explorer II 216570 
is that (as stated earlier) Rolex made a tribute to the first Explorer 
II 1655 by adding "Phantom" hands on the new model 216750. However, in 
my opinion the blackened parts should have been matte instead of glossy 
which does not match the matte (Rolex calls it "satin finished") black 
dial of dial. Furthermore, the hands of the black dial new Explorer II 
have unequal amounts (i.e.: not the same length) of black pain on the 
hour, minute and GMT hand which spoils the design in my opinion.
Here compared with the Explorer II 16570 where you also get a feel of the size difference:
Like the "Phantom" hands on the Explorer II 1655 were 
re-interpreted, the big orange "Freccione" hand was re-
introduced
 on the new Explorer II as a historical nod. This even seems to be 
emphasised on the booklet that accompanies the Explorer II 216570:
The big orange 24hour hand looks beautiful together with the orange 
"Explorer II" writing, although I must admit that I the orange writing 
on white dial could have been made bolder like seen on the black dial 
version:
On the predecessor model 16570 (white dial) you could often notice poor 
quality control of the black painted hands. Notice how the sides of the 
hands are not painted perfectly:

(Photo by Jocke).
With the new Explorer II, Rolex seems to have paid more attention to this quality control issue:
The hands, markers and GMT hand are now "Maxi" style and emit the 
"Cerachrom" blue lume like on the new Submariner Date, Deepsea 
Sea-Dweller and Explorer 214270. The lume is fantastic and lasts all 
night (8+ hours), although not as intense as seen on this photo where I 
"charged" my Explorer II under the sunlight:
SCORE: 
6. MOVEMENT
Rolex manufactured a new movement for the Explorer II 216570: 
The Cal. 3187, featuring the inhouse Paraflex shock protection system and Parachrom Bleu hairspring.
The Cal. 3186 in the GMT II 11671x also has the inhouse Parachrom Bleu hairspring... 
Now, the question is: Both featuring a GMT feature, is the Cal. 3187 
identical to the Cal. 3186 apart from use of the inhouse shock system 
instead of using the outsourced (SWATCH Group) KIF system?
Answer is Yes... and NO.
Thing is, that the main plate of the Cal. 3187 is bigger than the one of the Cal. 3186:
- Cal. 3186: 28.5mm
 
- Cal. 3187: 30.97mm
 
Where most other watch companies introducing a bigger watch model would 
simply use movement spacers to make a small movement fit into a big 
case, Rolex did not compromise: 
They made the movement bigger, too! This is what makes Rolex so special!
One could argue that the Deepsea Sea-Dweller is 44mm, yet it still has 
the Cal. 3135 (with the blue hairspring) inside. So why did the Deepsea 
not receive a bigger movement? Because - combined with the Ring Lock 
system and Titanium caseback, the Deepsea also has a thicker case (more 
"meat") around the movement to cope with the 4,875 metres it's tested to
 withstand under sea-level.
The Cal. 3187 has got to receive the following score:
SCORE: 
7. ACCURACY
I have owned various Rolex watches with the inhouse Parachrom Bleu hairspring:
- Rolex Daytona 116520 (x 2)
 
- Rolex GMT II 116710LN
 
- Rolex Milgauss 116400GV
 
- Rolex Explorer II (M-series with Cal. 3186)
 
- Rolex Deepsea Sea-Dweller 116660 (x 4)
 
- Rolex Submariner Date 116610
 
ALL of the above ran slow (typically minus 2-4 seconds/day) straight from the box.
The Explorer II 216570 that I own now has been gaining .5 seconds since 
day one! Consistantly! It does not get much better than this, so it has 
to get this score:
SCORE: 
8. SUMMARY
To summarize, the Rolex Explorer II 216570 got the following scores:
- History Of The Rolex Explorer II
 
- Case: SCORE: 

 
- Bracelet: SCORE: 

 
- Crystal: SCORE: 

 
- Dial And Legibility: SCORE: 

 
- Movement: SCORE: 

 
- Accuracy: SCORE: 

 
- Summary
 
Evidently, it got a 99.99 positive score. Only slight gripe I have is 
the (in my opinion) too faint orange "Explorer II" writing on the dial.
In my opinion, the Rolex Explorer II is the best executed model that 
Rolex has released for a long time! It's an instant classic that I can 
recommend highly!