It's the usual story: they were supposed to come up with a cheap and small wristwatch but ended up creating a hit and a culture icon that has lasted for decades. The F-91W was Ryusuke Moriai's first design for Casio. Wonder if he got praise? Everyone should own at least one of these.

Rudimentary features

• Stopwatch
• Alarm Clock / Hourly Signals
• Simple calendar
• Backlight

The F-91W is famous and doesn't pick sides: it's distinctly the only brand-accessory ever photographed on Osama Bin Laden but has also been worn by a certain Barack Obama.

It's also well-known that this exact module has seen a lot of use as a timer in nefarious devices; it's cheap, instructions for modding are easy to find, and these are sold by the millions every single year. Any item this popular is next to impossible to trace, and seeing a random person wearing one doesn't really help profiling at all. The F-91W just floats everywhere like some kind of a Casio spirit, and its steadily beating quartz heart is only concerned with keeping time.

You would think a model this old would be obsolete, and when it comes to features, that is correct. However, very few watches are so astonishingly lightweight and small, yet accurate and reliable. Other watches may have armor and cushioning but the F-91W has another strategy: it's too small to hit with anything and it doesn't snag and bump thanks to the low profile.

The suffix 1YER means the color code (1 for Black), and the letters denote production series and sales region. The various regions are most often just packaged a bit differently, and the manual language varies.