F-91W

Introduced in June 1989 as the successor to the earlier F-87W, the F-91W began as just one of many budget digital watches in Casio's catalogue of the time, designed by Ryūsuke Moriai in his debut as a designer for the company. At launch, no one could have predicted it would become one of the most produced and best-selling watches in the history of watchmaking: over the decades production has surpassed hundreds of millions of units, making it one of the most widespread models ever made, digital or mechanical.

The secret to the F-91W's success was never technical, but a matter of balance: an extremely light resin case (just 21 grams), an integrated resin strap, a clear LCD display with calendar, chronograph to the hundredth of a second, daily alarm and hourly chime, all powered by a single CR2016 battery with a stated lifespan of several years. No superfluous features, a list price that has always remained very low, near-total reliability: characteristics that made it an "invisible" watch in the daily lives of generations of people worldwide, from the 1990s to today, with a design that has remained essentially identical to itself.

This very widespread ownership gave it, over time, an unexpected and in some ways paradoxical notoriety: in the 2000s the F-91W was repeatedly linked by international media to possible use as a timer in improvised explosive devices, to the point of repeatedly appearing in documents relating to detainees at the Guantanamo base as presumed evidence of affiliation. A controversial chapter that has not, however, dented its popularity, while unofficial imitations remain numerous to this day precisely because of its low cost and instant recognizability.