The Seiko 7A28 was the world's first analog quartz chronograph movement. It was a triple register chronograph capable of measuring down to 1/20th of a second with a rather unique single-handed split seconds mechanism. The movement has a power reserve of approximately three years and is designed to be highly durable, with shock resistance and water resistance up to 100 meters.
The Seiko 7A28 movement was used in several Seiko watch models, including the iconic Seiko 7A28-7000, which was worn by Sigourney Weaver in the movie Aliens. The watch's distinctive design and innovative features have made it a sought-after collector's item among watch enthusiasts.