1972 –Synchronar (also for 1975, 1977, 1981 and 2007)

Independent inventor Roger Riehl designed the most advanced wrist timepiece devised up to that time. His goal was to built an extremely accurate timepiece that required no service, could withstand great variation of temperature, was shockproof, was waterproof to great depths, was visible in any lighting conditions, and had multiple functions. In short, his goal seemed to be to build the ultimate wristwatch that would simultaneously overcome all of the traditional challenges to the wristwatch.

The inventor’s approach to the module was innovative. The Lexan plastic case is completely sealed – there are no openings in the case to allow a stem or push or battery. Small magnets on the outside of the case adjust the time. Adjustments to the time and the triggering of the LEDs for time display are made by magnet.

The Synchronar was introduced in 1972. Early models were purchased by the Hammacher Schlemmer store in New York City and sold through their catalog.
Of all the watches displayed on this site, it is the only model that has been in almost continuous production since its introduction – over 30 years ago. Few wristwatches have been in production as long. There have been three subsequent models of the Synchronar:

The Mark II was introduced in 1975
The Mark III was introduced in 1977
The Mark IV was introduced in 1981

The features of the Synchronars have become more complex over time. The Mark IV model has the following features:

  • Hours, minutes, seconds
  • Two time zones
  • 12 or 24 hour models
  • Calendar to year 2100
  • Timing adjustment of up to 8 seconds a year
  • Daylight saving adjustment (The spring date is set at last week in April as designated at that time. Four years later, the spring date was changed to the first week in April. This was not reprogrammed in the model but the daylight savings feature can be switched off.)
  • Alarm
  • Stopwatch
  • Flashing timer

    Later versions of this watch had a thin sheet of stainless steel on the back of the Lexan case so that the plastic was not in contact with the skin.
    The Synchronar is based on a timing system that, to my knowledge, in unique – it is an adjustable quartz watch. Reihl called this “Digital Synthesizer Adjustment.” The watch can be adjusted plus or minus 8 seconds per year by the user. In the instructions for the Mark IV the technical benefits of the synthesizer system are described:

    The Synchronar watch uses an exclusive digital adjustment scheme which can be reset by the owner… Since the quartz crystal is not tuned by a tuning capacitor as in all other watches, we do not have the temperature and vibration sensitivity of this component to affect the stability or accuracy. Also, the energy level for the quartz crystal oscillator is lowered by design because we do not have to allow for tuning away from the optimum stability frequency. In other words, our watch oscillator depends less on unstable external components and more on the mechanical resonance of the quartz.

    There has been some variation in the case design over the years and the cases were offered in a variety of materials – stainless steel, black ceramic, gold, gold plate, and titanium. All the Synchronars shown on this website are the same example of a Mark IV (except the “kit” model shown under Post 1995) because the cases for the various models looked similar.

    The design of the case of the Synchronar is one of the features that makes the watch unique. It did not copy any other watch design and no other watch design has copied it. The design was so unique it was patented. (Filed, April 20, 1972, Ser. No. 246,122. Patented, November 6, 1973, Des. 229,085) Below is a copy of the patent document.


    Roger Riehl was working on the Mark V circuitry when he died in 2005. He was considering a number of advanced features such as multiple time zone functions, alarm, moon phase, and sidereal time function. He was also considering a box for the watch with a light in it to keep the watch charged, including a copy of Pieter Doensen’s book Watch, and a circuit diagram of the Mark I.

    The Legacy Edition was produced beginning in 2006. One of inventor’s sons, Howard Riehl, began a limited production run of the watch again following his father’s death. This is a continuation of the production of the Mark IV model and is offered in limited numbers. It includes one of the improvements made to latter examples of the Mark IV. It has a stainless steel panel on the back of the watch module so that the skin does not directly touch the Lexan case back.

    In addition, Howard Riehl has also begun to sell Synchronar “kits.” These are new working Synchronar modules that fit into older cases. These modules have not been sealed or filled with any potting material. The modules can be temporarily sealed and reopened to replace the battery if necessary in the future. Mr. Riehl can be reached at riehl_synchronar_2100@yahoo.com and his website is http://www.riehlsynchronar.com/official_info_site.html

    The watch shown under “Post 1995” is a Synchronar kit watch purchased in 2007. The module is a clear plastic case with a Mark IV integrated circuit and new solar cell, batteries and quartz crystal. The case is titanium case with angular edges.