It’s Back! ― A Review of the Synchronar 2100 Mk IV “and a Half”

by anachronicler


About This Review

I wrote this review back in March 2003, and Guy Ball was kind enough to publish it on his website Unfortunately, his excellent site ceased to exist some years ago, so the original review is no longer there. I even failed to locate it with the wayback engine at

Since I have the impression my review attracted its fair share of attention at Guy’s site, since I did put quite some effort into writing it, and since I happen to have saved a copy, I thought it would be a good idea to publish it again.

…and here it is!

Please note that 15 years have passed since I wrote the original. For this reason, I found the following actions appropriate:

  • I have read it again, to make sure that I still stand for what I wrote back then.
  • Some more or less necessary corrections and remarks have been added [in square brackets].
  • Hyperlinks gone stale are marked brown and underlined. The content they referred to could still be out there somewhere, but I have not found the energy to hunt them down.
  • I have not bothered to add comments about the end of the story, all that happened to this watch after the original review was written. (If you have to know, some of that is actually included here and there in earlier chapters of this blog.)
  • Roger Riehl, the designer and builder of the watch described, died only a few years after the review was written. His company, essentially a one man operation, disappeared with him. I have not commented every individual part of the text, where this sad fact makes the original text incorrect. Please keep in mind that the text is 15 years old (at the time of re-publication).
  • You don’t agree with me, and miss the comment field below this review? Well, everybody is entitled to his/her opinion, but it’s not one of the fundamental human rights to have it published everywhere. Feel free to comment on the review, but do it elsewhere.

The original review follows below the line:


  1. Introduction, Short Description of the Synchronar
  2. Packaging, Delivery
  3. Appearance, Design, Finish
  4. Technology, Performance
  5. User’s Manual, Ease of Use
  6. Verdict, Conclusion, Overall Value
  7. Contact Info

Introduction, Short Description of the Synchronar

The watch under scrutiny is a Synchronar 2100 Mk IV “and a half”, one of the about two dozen that made up the first batch of watches released from the RTC Division of the Custom Circuits Corporation during this millennium. The bracelet delivered together with my watch, the “deluxe band” as it was called on the order form, has been manufactured by Hadley (= Hadley-Roma today?), but will be covered by the review anyway.

The first Synchronars hit the market in the early seventies, and the construction has been improved incrementally ever since. The history of Roger Riehl and his brainchild, the Synchronar, is already covered by an interview article written by Guy Ball, so I will not duplicate that effort here.

There is as yet no Mk V, it is still in the RnD pipeline. The Mk IV has, however, been improved so much since it was released, not least between the previous batch and this, that Roger jokingly called it Mk IV “and a half” during one of my telephone calls with him. It is easily told apart from earlier Synchronars by the stainless steel wafer glued to its back. Earlier incarnations of this watch exposed “bare” Lexan to the skin of the wearer.


Anyway, the main characteristics of the Synchronar are:

  • digital LED display
  • solar powered, the first wrist watch ever to be so
  • hermetically sealed, in the strictest sense of the word, and filled with rubber

Features offered by the Mk IV (see also Technology, Performance below):

  • time: hour, minute, seconds, month, date, weekday, leap-year
  • second time zone
  • perpetual calendar (requires user input every three out of four centuries)
  • alarm (visual)
  • chronograph, up to 24h with 1/100 precision, split time, and elapsed time flasher
  • quartz precision with user correctable rate in steps of ± 8 sec./ year (without breaking into the watch!)
  • pressure resistance to diving depths of 280 m (750 ft)

Packaging, Delivery

Considering how well it was protected for the shipping (U.S. → Hamburg, Germany), I almost started to have second thoughts about the ruggedness of the watch. No, seriously, it was very well packaged. First one cardboard box, almost completely covered by packing tape. Then a thin layer of Styrofoam “digits” keeping the next cardboard box away from the outermost box. Embedded in a second, thicker, layer of Styrofoam digits there was, finally, a black, vinyl-covered cardboard box containing the actual watch box.


The innermost container is a metal box covered with black vinyl. Its lid is padded on the top and is held shut by a spring at the hinge. “Clop, clop”, like the boxes for old shavers. No big wonder, the box probably is from the late seventies. Additional circumstantial evidence: How else could the watch-holder inside be a piece of felt-covered metal instead of plastic? To be perfectly correct, the entire box is metal! Except for the text on the big metal stickers, the innermost looks just like vintage Synchronar boxes.


I like it. It harmonises well with the watch (see next section).

Less charming is the amount of printed material delivered with the watch. Two photocopies of a double-sided, single sheet instruction manual, and a b/w picture of a Synchronar (though on real photo-paper). Fortunately, Synchronar enthusiasts have scanned owner manuals and published them on the Internet. They provide information on solar power (dis-)charge times, watch care, and some additional info on the technology used in the watch. The instruction sheet included with my watch only explains how you activate the various functions of the watch, how to set it, and how to adjust the rate of it. Oddly enough, the watch came without any guarantee document.

It would have been nice if it had taken less than three years and two months to make the watch. Nicer yet, if Roger had told me so from the start. His method of keeping his customers off his back for two months at a time—by telling them about new, unforeseen, two-month delays every time they call—ran extremely dry of credibility after about a year.

Section Summary

Positive points are awarded for

  • safe packaging
  • retro (looking) boxes

Negative points are awarded for

  • cheap-looking documentation
  • insufficient amount of documentation
  • missing guarantee statement!
  • lack of feed-back considering the time of delivery
  • record breaking slow delivery

Appearance, Design, Finish

Few, if any, watches look like the Synchronar. I have a handful of watch enthusiast books, and a number of watch magazines and catalogues, but it is only with utmost difficulty that I can find any watch therein that resembles the Synchronar even remotely. Among ordinary watches it is a certain attention-grabber. Here pictured together with my Longines Conquest V.H.P. (1996 model, without perpetual calendar):


[The Longines was stolen by burglars a few years ago. ☹]

On the wrist of Captain Kirk, it wouldn’t raise an eyebrow, though, if you get my point. To say the design is sterile would be wrong, but I have to admit it looks “engineered” rather than designed. The Synchronar is actually a rather chunky watch, but today, when “oversize” watches are still selling surprisingly well, this is no handicap. Due to its squarish shape, it is a large watch for its size, 40.8 × 38.5 × 11.8 mm. At the same time, it is streamlined enough not to catch and damage shirt sleeves or knitted sweaters. It also lacks a crown that could dig into the back of your hand when you, for instance, lean on a table. So, paradoxically, it is also a small watch for its size.

Unlike most other watches, digital in particular, it has a very quiet, even secretive, look. There are no symbols, scales or pointers that disturb the visual peace, and the time is only displayed on demand. It’s a pity that the Swiss micro-electronics wizards haven’t had a chance to get to work on this watch. Making it half as thick as today—more would hardly be needed with today’s technology—it would look cooler, sleeker, and smarter.

The bracelet certainly has the looks to match the watch. The brushed stainless steel finish is the same as that of the watch, the physical dimensions balances the size of the case. The design looks definitely contemporary to that of the watch, making it potentially difficult to find a suitable replacement, should the need arise.


The watch, the bracelet, the box—everything looks as if they have been sitting around on a shelf for the last thirty years, and many of the parts probably have! It’s a collector’s dream, almost, but you have to pinch your arm repeatedly in order to sober up and tell yourself that it was actually assembled in the 21st century.

Now, let’s get picky, let’s talk about the finish of this watch. Personally, I have adopted the following “objective” measure of the level of finishing of wrist-watches. The answer to the question “How much magnification can the watch take before revealing its imperfections?” is defined to be the “Visual Level of Perfection”, VLoP. Somewhat disappointingly, the Synchronar does not even pass 1 VLoP. That is, several imperfections are clearly visible to the naked eye.

First of all I noticed that the bond between the plastic lid and case was less than perfect, with a visible crack in which some polishing compound remained. It starts at the left edge and ends under the third digit. There is a similar crack on the opposite side.


Then, the first time I let the light reflect from the solar cell, a row of bubbles, trapped between the window and the cell, became clearly visible.


Good thing then that the largest cavities are only visible at very special combinations of viewing and illumination angles.


A closer look reveals that there is a large number of miniscule bubbles behind the window in addition to the “main” cavities. They are not only there, they can also be found in front of the digits in the display. You don’t really think about them when you take a glance at the time, but after discovering them, I cannot help speculating on how crisp the display would have looked without them. This close-up photograph doesn’t really make them justice, there are more of them in reality.


Talking about the display, I have found that it is ever so slightly, but still perfectly perceptively, tilted with respect to the outer stainless steel cage. The hour end of the display is slightly closer to the top of the watch than the minutes end. The outer edge of the light well serves only too well as a reference for the critical eye.

The metal cage surrounding the plastic module is not perfect either. The brushed metal finish reaches over the edges of the facets in some places, leaving these spots brushed the wrong way. And—isn’t it time to plug that hole at the back of the cage? After all, the sliding magnet switch that used to sit behind that hole was done away with some twenty years ago.

The bracelet only looks solid at a distance. Close up, it becomes apparent that it actually seems to consist of a large number of strip metal snippets and pins that have been cleverly folded/welded?/stamped together to form the links of the bracelet. The clasp looks genuinely outdated, or cheap, to put it bluntly. Maybe I am spoiled by all the solid, CNC-machined bracelets of modern watches. Note the traces of corrosion(?) near the hinge in the below close-up. Is it just traces of something that wasn’t polished away or did it appear afterwards?


Some corrosion (or grime??) was also visible on the connector pins of the length-corrector links. Maybe not surprising, when one thinks of how long these things have been sitting around in various ware-houses.

How many VLoPs, what level of perfection, is it fair to demand? Well, I am certain that few wrist-watch enthusiasts would accept anything but jewellery finish on a new, non-cheap watch.

Section Summary

Positive points are awarded for

  • radical looks
  • as if delivered with a time machine from the early seventies
  • not a shirt-sleeve eater

Negative points are awarded for

  • flaws, flaws, flaws—finish below [current] normal watch standards
  • primitive-looking bracelet
  • too chunky

Technology, Performance

When contemplating the sub-system technologies that are combined in the Synchronar, I get a strong feeling that this particular “brew” is one of the few solutions there are to the LED watch problem. The different technologies interlock nicely, making the end result greater than just the sum of its parts.

The key to this solution is solar power, it provides all the power that the LED display needs. Now we have a watch that does not need winding, nor battery changes, and contains no moving parts. So what would be more natural then than sealing it up for good and fill it with, say, rubber? That would, after all, protect the inside from the dirt and moisture on the outside. Permanently! No more worries about water intrusion, no more worries about seals going bad over the years.

Filling it completely with a soft rubber also leads to excellent pressure resistance virtually for free. As the rubber is about as incompressible as the water in the ocean, the case does not have to be dimensioned to take the pressure. The line of defence is moved into the watch, and the outside pressure now acts on each individual component inside the watch. Thanks to their small size, and solidity in many cases, they can take a lot of pressure without further modification. Eventually, at around 300 m immersion, the batteries will start to leak. The bubbles trapped in the rubber [of my watch] are probably far too small to make any difference to the ultimate pressure resistance of the watch.


What are the drawbacks? Yes, you have to slide a switch to see the time, and yes, you may have troubles seeing the digits under some light conditions. With respect to the latter, I think the Synchronar must be one of the best LED watches ever built. The display is sunk deep into a light well, just like the instruments in the dashboard of a modern car, so it usually does not take much of an effort to keep the display in shadow. This picture shows how far into the watch the display is situated, at least 3 mm.


In addition to this, the light intensity of the display is adjusted in three steps to match the ambient light levels (and save battery power when possible). I have been told that future models will feature a fourth light level with “unlimited” intensity. (When activated, the solar cell will be disconnected from the battery, feeding the display with all the power it can deliver.)

Finally, the contrast of the LED display is enhanced by the filtering effect provided by the red plastic in front of the LED digits. The end result is that the display looks too bright indoors, OK outdoors, adequate in direct sunlight, and unreadable when the sun strikes directly on the display. Sunlight + haze is also hard on the contrast, since there are no shadows, not even in the light well of the Synchronar.

Here we should remember that many watches with hands also have their bad moments when it comes to readability. “Passive” paints loose their zap after a few hours, polished hands can become “invisible” if they happen to reflect something with the same colour as the dial (not extremely uncommon with a white dial, since ceilings and clouds often are white). So, I think a LED display is not as great a handicap as many would like to think, at least not when proper design measures have been taken to boost contrast.

Being an engineer—or control freak, if you like—I definitely appreciate the owner-friendly rate correction procedure. No tools, no guesswork—the rate setting is as easy as setting the alarm. Easier, to be perfectly honest!

The alarm function is charmingly useless. I have missed it every time so far. How come? It is mute! If you don’t happen to catch the discrete blinking in the corner of your eye—forget full length sleeves—you’ll miss it.

Another charmingly eccentric feature is found if you push the left-hand slider away (from the display) and “jog” it once. This corresponds to “double click” in mackintoshese. This brings you to a state that will show you a single “:”. Now what is this? A quick chat with the manufacturer reveals that this state is there “in case”. In case, that is, Roger decides to add a chip at the corresponding empty piece of real estate that has been left “in case”, a chip that can deliver something to be displayed—temperature, barometric pressure, compass heading, whatever —in place of that “:” that the “Curious George” is rewarded with today. I seriously doubt that any modern consumer electronics has a user interface that is as close to the hardware as this. They have a nice, comfy layer of software between the user and the hardware, presenting a consistent and crack-free facade to the outside world.

One of the sliders tended to stick at one of its endpoints. This turned out to caused by a tiny superfluous slither of plastic under the slider, leftovers from the moulding process. Once removed by a sharp hobby knife it worked perfectly. This slider is shown upside down in the following picture, with its ‘track’ in the background. (The ‘bonus’ plastic was at the edge of one of the circular marks.)


This success made me turn my attention to the other slider. In comparison with the one I had trimmed, it had a somewhat gritty feel to it. Sure enough, closer inspection revealed that it was trimmed to, albeit not as carefully as the one I had done. The “belly” of this slider was no longer flat, making it ride poorly on its track. A tiny fraction too much material had been removed, making the knob of it a wee bit harder to catch with the tip of the finger. The difference in smoothness vs. grittiness will surely disappear after some wearing in of the slider tracks, and I think I will manage to ignore the miniscule difference in haptic functionality.

Talking about sliders, the magnetic switch on the left-hand side of the watch, closest to the display, is not sensitive enough. It doesn’t really matter why, it noticeable anyway. That particular switch is used, among other things, for starting and stopping the chronograph. When doing that in a hurry, which can be the case when using that particular function, the switch doesn’t get the message. Cross-checking the symptom by catching a few split times with the right-hand switch, revealed that I wasn’t mistaken. It works only when the slider is allowed to rest at the end-point for about a quarter of a second before it is released. (The chronograph is started/stopped on release.)

The last link connecting the bracelet to the back of the watch had an annoying tendency to catch on something behind the spring. Sure enough, there was a piece of plastic in there. It had been trimmed down by hand tools—how is that for hand-made, eh?—but not enough. A call to the manufacturer revealed that the annoying piece of plastic served no purpose in the Mk IV and that it would be safe to trim it some more. The trusty hobby knife was brought into service once more. The following picture shows this plastic ledge, as well as that silly hole that isn’t used any more.


After dismounting the bracelet for this treatment, I noticed that the spring-loaded pins that hold it in place were quite short. So short I couldn’t put my mind at rest before they had been replaced. The manufacturer will tell you that they are very special, since they are 100 % stainless steel, and that “normal” bracelet pins are only made of brass. He may be slightly out of tune with the progress of modern watch making—the people in the watch shop were I bought the 1.8 mm gauge pins didn’t even blink when I asked for 100 % stainless pins of that dimension. This observation is supported by the result of a quick search for pins on the Internet.

The following picture shows one end of one of the bracelet securing pins as it rests on the back of the watch, right above its hole. The other end is pushed firmly into its hole. As you can see, the margin before a potential “drop-out” is very small indeed. The tics on the scale mark millimetres.


The clasp has already showed tendencies to snap open. No big surprise, it has none of the clever double or triple security locks that are common on better watches of today. I don’t want to lose this watch, so I will surely try to replace the clasp for something better.

It also bothers me that the watch is so different, such a niche product, that you can only get repairs/spare parts from one source in the world. Remember that the watch filled with rubber and glued shut. You cannot go to any watch maker or micro-electronics expert to get it repaired, you have to find someone who knows how to break into the watch and how to close it when the actual repairs are done. This anxiety had been far, far lesser had the producer been a reasonably big company with a decent chance of surviving the next 50 years—after that, I certainly won’t care  ☺—but the current source of Synchronars, the RTC Division of the Custom Circuits Corporation, may very well cease to exist once the creator of the Synchronar, Roger Riehl, decides to retire.

Section Summary

Positive points are awarded for

  • second to none when it comes to water-resistance (not pressure resistance, though)
  • possibly very, very, robust
  • user correctable rate to within ± 4 seconds/year from correct rate
  • decent readability
  • no battery replacement, no spring run-downs

Negative points are awarded for

  • bracelet end getting caught on protruding plastic
  • sticky slider
  • short bracelet pins
  • fluky chronograph switch
  • spare parts? serviceability?
  • useless alarm
  • unsafe bracelet clasp
  • watch out for solvents!
  • Are the trapped bubbles etc. signs of a general production problems or just superficial flaws?

User’s Manual, Ease of Use

As stated previously, the manual delivered together with the watch is no more than a double-sided US-Letter page of text. Thanks to the relative simplicity of the watch—no compass, no barometer, no computer interface, only one split time, etc, etc—this is sufficient, but it sure helps to have the watch at hand when reading it.

The limited communication channels make the usage potentially taxing on the user’s ability to keep track of the inner state of the watch. The sliders can be pushed to two positions each, obviously requiring the user to execute clever juxtapositions and sequences of slider movements in order to reach some of the more well-hidden functions of the watch. The watch responds by using equally clever combinations of lit/unlit/blinking segments of the display.

The basic time display looks like this:


This is used for first and second time-zone, alarm time, chronograph time and split time. The display will shine steady for ordinary time, blink once per second when displaying the second time zone, and blink twice when showing the alarm time. The chronograph functions are so far separated button-wise from these three basic time functions, that there is no reason for optical signatures for them.

Now that I think of it, the month:date display looks the same as the basic time display and just happens to be activated by a similar slider movement. Well, well. If you and your fingers suddenly forget how to activate the most basic function of them all, and happen to mistake the date for the time, I guess you’ll have serious troubles with many of the other functions. (…until you turn sober again  ☺ that is)

The day/seconds display looks like this:


The “Alarm off confirmation display” is shown in the below picture. The builders have told me that future models will display “OFF” instead, making the watch somewhat easier to understand.


The following picture is a toughie. Here we see that the watch has reached the third year in its four year leap-year cycle (the first digit), and that its rate has been adjusted to speed #673 (the following three).


Never having managed to develop any fear for technology in general, nor push-buttons in particular, I may be the wrong person to give a verdict on this, but I think it doesn’t take superhuman skills to learn and remember how to use this watch. There is certainly no need to print “mode”, “set” and other eye-sore words on that plague many digital watches. (Apart from lack of need, it would be impossible to do so since the slider positions take on several different meanings depending on the situation. Personally, I think printed instructions like that should only be needed on stolen watches. The owner should be familiar with his own watch.)

Most of the functions are reached through fairly simple and logical slider moves. There are some exceptions. Let’s warm up with a minor one. Contrary to mechanical chronographs, it isn’t possible to time an event right away with this watch. It has to be switched over to chronograph mode first.

OK, that didn’t convince you. Time for the heavy one. The watch has an Elapsed Time Flasher mode. When activated, the watch will show you the current hours and minutes elapsed since the chronograph was started, two seconds every ten seconds. It can only be activated from chronograph mode and only when the chronograph is running. Furthermore, the elapsed time is flashed only when you are in chronometer mode. So, if you are timing a long time event, and have switched back to chronometer mode (with the chronograph still running, of course), and happen to decide that you would like to activate the ET-flasher, you must do the following:

  1. Pull left switch forward, then the right-hand switch too in order to switch over to chronograph mode.
  2. “Triple slide” the right switch towards the back of the watch so that the ET-flasher is enabled.
  3. Slide both switches away to go back to chronometer mode.

Changing your mind and switching it off takes just as many moves, except for one extra slide in step two. Not the best thing to do while driving. In my opinion, it would have been nice to be able to turn the ET-flasher on/off from chronometer mode. It would be equally nice to be able to see it from chronograph mode.

One final word about the ET-flasher mode. The current (and older) versions of the Synchronar may protect themselves against battery run-down by refusing to light the display when the battery voltage has dropped to low, but this does not include the ET-flasher mode. If started and not manually interrupted, it will go right ahead and drain the batteries completely. Current time, date, leap year, rate setting—everything will be forgotten. Future models may lack this suicide feature.

The Least Used and Hardest to Find Feature Award goes most probably to the automatic daylight saving time enable/disable function. Close to the date setting? Near the month setting? No, it is right where the minute setting of the second time zone would have been, had there been such a thing. Good thing that this watch has a fairly limited number of features. It doesn’t take too long to hunt down features that have “disappeared”. Shorter time than it will take you to dig up the instruction sheet, to be precise.

Automating the activation of daylight saving time—without relying on radio receivers as in all those atomic clock controlled watches—seems to be a rather hopeless watch feature to pull off successfully. The dates for the fast forward/backward hours differ from country to country, and they sometimes change. The current incarnation of the Synchronar 2100 Mk IV has its DST dates programmed to fit a set of US rules that never made it through the political treadmill. This means that this feature certainly will not work in the states. I have already noticed that they do not fit the German DST dates either. If I happen to find a country that fits the bill, I will certainly update this review. [No I won’t.]

Setting any of the “primary” functions of the watch—time, weekday, rate, leap year, date, month—takes a little practise. Not the act of making the right moves with the switches, but developing the required concentration and reflexes to make it on the first try. After the initial delay of ca 6 seconds, the hour, minute, whatever, springs to life and ticks away at a rather good clip. If you had planned to make a “one click” correction, you are often caught by surprise, and have to try to catch the desired value on the second lap instead. It would be nice with a slightly more gradual acceleration here.

The “double clicking”, or “jogging” of the switches that is needed to reach many of the functions, has to be made fairly rapidly. I may have slow muscles, but it is annoying to get a re-run of the previous readout instead of reaching the intended function.

The sliding switches takes some getting used to. They have a rather dead feeling, not at all like the trigger on my camera. Well, well, few digital watches have. So far, however, it has been disturbingly difficult to operate the sliders with wet fingers. With merely wet fingers, the friction between the steel cage and the fingertip makes it hard to slide the finger at all. Thoroughly wet fingers seem to slip straight over the slider.

Section Summary

Positive points are awarded for

  • most of the functions are activated by fairly logical slider manipulations
  • the visual cues offered by the display helps the user understand what he/she is doing
  • the automatic DST functionality can be turned off

Negative points are awarded for

  • the automatic DST functionality must be turned off since it probably won’t work where you live
  • starting (or stopping) the chronograph timer is not a straight-forward undertaking, if you start from chronometer mode
  • setting is like pouring ketchup

Verdict, Conclusion, Overall Value

After a long time of complete absence from the high status market segment, the time is certainly ripe for a comeback of digital watches. Personally, I think that the pendulum has already passed the turning point. During the last two, three years, some very interesting digital wristwatches have appeared on the market, such as the Ventura v-tec alpha, the Sjöö & Sandström Ocean Race Chronograph, and the Tag Heuer Microsplit. [The two latter are no longer produced.]

I think the Synchronar has the potential to battle adversaries of this calibre. It has got a history with mythical qualities suitable to build the brand name aura that is needed. It has got the looks to be remembered by the potential buyer. It also makes use of some eccentric technology that sets it apart from the competitors.

There are a couple of things that must be dealt with first, however. The fan-club will always buy this watch, but the ordinary watch-lover will demand near impeccable finish. The crazy bunch may put up with unspecified waiting times that stretch to over three years. This may be part of the experience/myth-making/whatever, but the average buyer will simply not put up with conditions like that. Massive efforts to regain a good reputation on the market are most likely needed.

Final verdict? Well, it is very special watch, although not The Ultimate Watch, as some enthusiastic individuals in the fan-club appear to believe. Whether or not you think the Synchronar is worth the $500 I have heard it costs at the moment, is very much a question of how highly you evaluate finish and quick delivery.

Contact Info

[The contact info to the RTC Division of the Custom Circuits Corporation has been removed, since Roger and his company are no longer with us. Apart from the usual channels for person-to-person trading, your best bet for finding a used or new Synchronar 2100 is probably to vent your desires in the Vintage LED Watches, Synchronar forum at]