Roger Riehl wrote of constructing the first digital electronic watch in March of 1968. Time was kept with a piezoelectric tuning fork and the displays were Pinlites. The watch required a 5 to 6 volt power supply.
With advances in LED technology and integrated circuits using CMOS technology, his attention then turned to the more advanced concept of the Synchronar, a rugged, sealed module that was solar powered. Riehl completed this prototype of the Synchronar in 1970 according to the research of his son Howard.
Many of the design elements of the production version of the Synchronar are displayed in the prototype – the distinctive case and side view layout and the use of Lexan on the module. However, in this prototype the display is activated by buttons on either side of the case, not the sliding magnet switches on the top of the case Riehl used in the final design. The band is not original to the prototype. Riehl’s patent for the solar watch (#3,823,551) was filed May 3, 1971 and is available by link here.
Photographs are by Howard Riehl and used with his permission.