The American company, Bulova produced an innovative line of timepieces during the 1960s and 1970s: the Accutron.
Bulova's headquarters are in New York, USA; however, all Accutron watches were made in Switzerland (1).
Two of the most noticeable characteristics of the original Accutron are the extremely smooth sweep of the second hand and the hum of the tuning fork.
At the time, the tuning fork driven mechanisms of the Accutron were the most accurate consumer timepieces available, accurate to within two seconds per day.
The improvement in accuracy was largely due to the increased frequencies used by the Accutron movements - anywhere from 300 Hertz, ranging upto 720Hz in the movements licensed to Omega watches; most of the Bulova movements vibrate at 360Hz.
In comparison, the movement of a
traditional balance wheel watch oscillates at 4Hz.
Any disturbance to a traditional mechanical movement has a larger impact because of the relatively slow oscillation.
Traditional movements are more susceptible to changes in the consistency and quality of internal lubrication and friction surfaces. On top of that, the performance of traditional movements are more dramatically affected by the effects of gravity and temperature compared to the Accutron's tuning fork movement.
Later versions of the Accutron used quartz to regulate the electronics of the watch.
In some models, the tuning fork was still present, but served no part in the regulation of the circuit. Eventually, the tuning fork was removed altogether.
Modern-day Accutrons are now largely indistinguishable from any other quartz watch.
Tuning fork Accutrons only need maintenance every decade, opposed to every 5 years for other mechanical timepieces.
Finding spare parts for Accutrons is difficult, particularly the delicate ruby index wheels and coil assemblies.
If you have a working Accutron, treat it well.
Updated: 1st November 2003, added more detail.
References:
(1) http://www.bulova.com/about/faq.aspx:
Q: Is Bulova a European company?
A: No. It is an American Company. It was founded in New York City in 1875. Some of our products, however, do come from other countries. For example, all Accutron watches are Swiss made.
Other information largely from:
The Accutron Watch Page: http://members.iinet.net.au/~fotoplot/acc.htm