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This tuning fork-controlled, battery-powered wristwatch was the world's first truly electronic watch. It was designed by Max Hetzel and released in 1960. It used a precision tuning fork as a time standard instead of the traditional balance wheel and hairspring. The tuning fork ensured greater accuracy, and Bulova was able to guarantee that it would not lose or gain more than a minute in time a month. Until the advent of the quartz crystal-controlled wristwatch in the 1970s, the tuning fork watch was the state-of-the-art and was even used by NASA in its Apollo program. Many thought it would become the standard mechanism for wristwatches. It remained in production until 1976, by which time five million tuning fork watches had been sold.