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Seiko F231-5000

The world's second thinnest digital watch in 1979


In 1979, thin was in. At 5mm thick, Seiko's F231 was the second thinnest watch of its time and was Seiko's was of demonstrating its mastery of quartz technology.

The 1970s were very hard on traditional watchmakers and that period became known as the "Watch Wars" as new quartz watch technology pitted low cost semiconductor technology against the traditional high quality mechical movements. Many estabilished Swiss companies that were initially relucant to embrace quartz were soon scrambling just to survive. At the end of the 1970s, the Swiss were bent on showing that they not only could compete in the new digital era, but that they had the upper hand in technology. At the end of the 1970s, a war was on to produce the thinnest watch as a means to demonstrate technical dominance.

The Seiko F231 is a very refined watch. It features a 6 digit display, shows the day of the week using alphanumeric characters, and has a fine matching bracelet. The F231 is so comfortable to wear that you hardly even know that it's on. Because of its thinness, neither the F231 or any of the other ultra thin watches featured a backlight. One of the most unique features of the F231 is the technology used in the reflector behind the LCD display. The F231 features an LCD reflector made up of a square array of tiny pyramidal micro reflectors which makes the display easier to see from the side.


Case: Excellent.
Almost mint, with the original plastic sticker on the back. The brushing on the case front is original and the plating is all near perfect. All sharp edges are still crisp.

Face / Hands: Very good.
The reddish colored front face is in near perfect condition. The buttons have a few tiny marks from being pressed with a fingernail.

Crystal: Excellent.
No visible scratches or scuffs.

Band / Bracelet: Excellent.
This Seiko bracelet is original and in near perfect condition. (and very comfortable). It fits a full sized 8" wrist.

Function / Accuracy: Excellent.
All functions work perfectly. Digital quartz accuracy.