"Accutron" tuning fork watches, first sold by Bulova in 1960, use a 360-Hertz tuning fork to regulate a mechanical watch movement. It's inventor was Max Hetzel, who joined the Bulova Watch Company in 1948. Hetzel was the first engineer to use an electronic device, a transistor, in a wrist watch, and his Accutron was the first watch that truly deserved the adjective electronic. More than 4 million were sold until production stopped in 1977.
Few developments in timekeeping technology created a stir like the introduction of a watch that used a tuning fork as a timing standard rather than a rotating balance wheel. Eight years in development, the Accutron had only 12 moving parts and 27 parts total, compared with 26 moving parts and 130 parts total in a typical self-winding mechanical watch.
Accutrons are supposed to neither gain nor lose more than one minute per month. Prior to the Accutron, it was unusual to find a mechanical watch of this accuracy, even a certified chronometer.
Before Accutron, the method of keeping time mechanically had not changed much in over 300 years. Suddenly in 1960, a timepiece went on the market which was inherently accurate and made the use of escapements and balance wheels obsolete.
The original Accutron 214 is an American icon, born at a time when America felt threatened by Russian advances in space technology. It was brought into existence by Bulova under the leadership of retired general Omar N. Bradley, the WW2 hero for whom the Bradley Fighting Vehicle was named.
During the 1960's it was worn by most of the pilots of the X-15 rocket plane, and Accutron played a part in every US Space mission during the 60's and 70's including the Moon landings. There are several Accutron 214 timing devices sitting on the Moon's "Sea of Tranquility," placed there by astronauts.
The Omega Speedmaster Professional chronograph wristwatch (known as the "Moon watch") was designated by NASA for use by the astronauts in all manned space missions, becoming the first watch on the moon in the wrist of Edwin 'Buzz' Aldrin.
However all the instrument panel clocks and time-keeping mechanisms in the spacecraft on those space missions were Bulova Accutrons with tuning fork movements, because at the time, NASA did not know how well a mechanical movement would work in zero gravity conditions.
The Accutron 214 was declared the American "Gift of State" by President Linden Johnson and given to hundreds of visiting dignitaries. The 214 was made into panel mount clocks and installed in the instrument panels of thousands of military ships and aircraft including "Air Force One". The 214 can reasonably be considered the prototype for all modern quartz watches. No other timepiece has had a greater impact on the way we keep time today. (info from Finer Times, Bulova, Wikipedia, Accutron214)