:Casio F-91W

Designed by Ryūsuke Moriai as his first design for Casio,{{cite news|url=https://www.ablogtowatch.com/tokyo-man-designs-casio-g-shock-watches-ryusuke-moriai/|title=An Afternoon In Tokyo With The Man Who Designs Casio G-Shock Watches|publisher=[A Blog To Watch|date=April 16, 2017|access-date=July 6, 2019|author=Ariel Adams}} the case of the F-91W measures {{convert|37.5|by|34.5|by|8.5|mm}}. The case is primarily made of resin,{{Cite web|title=F-91W-1 {{!}} Digital {{!}} Youth {{!}} Timepieces {{!}} CASIO|url=https://www.casio-intl.com/asia/en/wat/watch_detail/F-91W-1/|access-date=February 16, 2022|website=CASIO Official Website|language=en}} with a stainless steel caseback and buttons, with the manufacturer's module number, 593, stamped on the caseback. The resin strap is {{convert|18|mm}} at the fitting and 22 mm across the widest part of the lugs. The total weight is {{convert|21|g}}.

The F-91W has a chronograph, featuring precision of {{frac|1|100}} seconds with a count up to 59:59.99 (nearly one hour). The chronograph is also able to mark net and split times (i.e. laps). Other features include an hourly time beep, a single daily alarm lasting 20 seconds and an annual calendar. The watch does not make allowances for leap years as there is no provision to record the year. Due to this, the month of February is always counted as 28 days.{{cite web|url=http://www.casio.com/products/Timepiece/Classic/F91W-1|title=F91W-1 Classic Timepiece|publisher=Casio|access-date=April 27, 2011}} The watch uses a faint green LED backlight located at the left of the display for illumination (in earlier units it was an amber microlight). According to the manufacturer estimates, the watch is reported to be accurate to ±30 seconds per month.

The quartz movement, designated Module 593, is powered by a single CR2016 3-volt lithium button cell rated to a stated battery life of 7 years.{{cite web|title=F91W-1 {{!}} Steel Black Digital Watch {{!}} CASIO|url=https://www.casio.com/us/watches/casio/product.F-91W-1/|website=CASIO Official Website}}

The front of the watch is marked "Water Resist". The black version (F91W-1){{cite web|url=http://www.casio.co.uk/products/timepieces/casio-collection//Product/F-91W-1XY/|title=F-91W-1XY|publisher=Casio|access-date=May 22, 2013|archive-date=May 30, 2011|archive-url=https://web.archive.org/web/20110530022746/http://www.casio.co.uk/products/timepieces/casio-collection//Product/F-91W-1XY/|url-status=dead}} is "30 meter / 3 bar" (i.e. 100 feet / 44 psi), the ISO standard meaning of which is: "Suitable for everyday use. Splash/rain resistant. NOT suitable for showering, bathing, swimming, snorkeling, water related work and fishing".

File:Casio F-91W 82T38575.jpg

The watch is controlled by three side-mounted push-buttons.

• The upper left button, labeled "Light", turns on the light, cancels the alarm, resets the stopwatch or marks the split (lap) time, and is used for selecting settings.
• The lower left button, labeled "Mode", cycles the modes of the watch: time display, alarm, stopwatch, and time/date adjustment.
• The right button, labeled "Alarm On-Off/24hr", is the function button: when used, it starts and stops the stopwatch, changes the settings currently being adjusted, or switches between the 12- and 24-hour modes, depending on what mode the watch is currently in.{{cite news|url=http://support.casio.com/storage/en/manual/pdf/EN/009/qw593.pdf|title=Manual|publisher=Casio|access-date=November 26, 2014}}

The time or date is adjusted by pressing the lower left button three times to bring the watch to time adjustment mode. The top left button is used to cycle through seconds, hours, minutes, month, date, day and normal mode. The right button is used to adjust the flashing value displayed. Unlike any other value, the seconds can only be zeroed. Should this happen before 30 seconds, the watch will zero in at the beginning of the current minute. After 30 seconds it will start the next minute as displayed. When the adjustments are finished, the bottom left button can be pressed once to return the watch to normal mode.

The watch display shows the day of the week, day of the month, hour, minute, seconds and the signs PM in the afternoon – or 24H (24-hour clock) – at all times, the alarm signal status (bar of vertical lines), and the hourly signal status (double beep on the hour, shown as a bell) are present when activated in the alarm mode.

In stopwatch mode, minutes, seconds and hundredths of a second are shown.

{{further|Seton Hall reports#Detainees' profile}}

File:Al Qaida watch timer on perf board 84071 -abc.jpg

The US government became suspicious of Afghans who wore Casio watches due to their ability to be used as timers for improvised explosive devices, a tactic favored by al-Qaeda.{{cite news|title=Guantánamo Bay files: Casio wristwatch 'the sign of al-Qaida'|url=https://www.theguardian.com/world/2011/apr/25/guantanamo-files-casio-wristwatch-alqaida|newspaper=The Guardian|date=April 25, 2011|first=James|last=Ball}}{{cite news|url=https://www.bbc.co.uk/news/magazine-13194733|title=Casio F-91W: The strangely ubiquitous watch|work=BBC News|date=April 26, 2011|first=Denise|last=Winterman}}

According to secret documents issued to interrogators at Guantanamo Bay, obtained{{cite web|url=http://www.theguardian.com/world/interactive/2011/apr/25/guantanamo-files-interrogators-al-qaida-taliban|title=Guantánamo files: How interrogators were told to spot al-Qaida and Taliban members|date=April 25, 2011|website=The Guardian|access-date=April 10, 2019|author=}} and released by The Guardian, "the Casio F-91W digital watch was declared to be 'the sign of al-Qaeda' and a contributing factor to continued detention of prisoners by the analysts stationed at Guantanamo Bay. Briefing documents used to train staff in assessing the threat level of new detainees advise that possession of the F-91W and the A159W, available online for as little as £4, suggests the wearer has been trained in bomb making by al-Qaeda in Afghanistan."{{cite news|first=James|last=Ball|date=April 25, 2011|url=https://www.theguardian.com/world/2011/apr/25/guantanamo-files-casio-wristwatch-alqaida|title=Guantánamo Bay files: Casio wristwatch 'the sign of al-Qaida'|work=The Guardian|location=London|author-link=James Ball (journalist)}} United States military intelligence officials have identified the F-91W as a watch that terrorists use in constructing time bombs.{{cite web|url=http://www.defenselink.mil/news/Nov2005/d20051104qahtani.pdf|title=USA v. al Qahtani|date=November 7, 2005|access-date=February 27, 2007|publisher=US Department of Defense}}{{cite news|title=Combatant status review board for Mohammed Ahmad Said el Edah|date=October 6, 2004|url=https://www.nytimes.com/interactive/projects/guantanamo/detainees/33-Mohammed-ahmad-said-al-edah/documents/5|work=The New York Times}}{{cite web|url=http://motherjones.com/news/feature/2006/07/detainee_sidebar.html|title=Why Am I in Cuba?|work=Mother Jones|date=July 12, 2006}}{{cite web|url=http://www.dod.mil/pubs/foi/detainees/csrt_mar05.pdf#216|title=Summary of Evidence for Combatant Status Review Tribunal|page=216|date=October 13, 2004|url-status=dead|archive-url=https://web.archive.org/web/20060731081044/http://www.dod.mil/pubs/foi/detainees/csrt_mar05.pdf#216|archive-date=July 31, 2006|df=mdy-all}}

This association was highlighted in the Denbeaux study, and may have been used in some cases at Guantanamo Bay.{{cite web|url=http://nationaljournal.com/about/njweekly/stories/2006/0203nj4.htm|title=Empty Evidence|date=February 3, 2006|work=National Journal|url-status=dead|archive-url=https://web.archive.org/web/20080704000658/http://nationaljournal.com/about/njweekly/stories/2006/0203nj4.htm|archive-date=July 4, 2008}} An article published in The Washington Post in 1996 reported that Abdul Hakim Murad, Wali Khan Amin Shah, and Ramzi Ahmed Yousef had developed techniques to use commonly available Casio digital watches to detonate time bombs.{{cite news|url=https://www.washingtonpost.com/wp-srv/national/longterm/twa800/bomb.htm|title=New Devices May Foil Airline Security|page=A01|newspaper=The Washington Post|first=R. Jeffrey|last=Smith|date=July 21, 1996|access-date=March 14, 2008|author-link=R. Jeffrey Smith}} Casio watches were mentioned almost 150 times in prisoner assessments from Guantanamo.{{cite web|author=Batya|date=July 9, 2020|title=How did the Casio F91W Become a Terrorist Icon?|url=https://reaperfeed.com/how-did-the-casio-f91w-become-a-terrorist-icon/|url-status=live|archive-url=https://archive.today/20200728060545/https://reaperfeed.com/how-did-the-casio-f91w-become-a-terrorist-icon/|archive-date=July 28, 2020|access-date=January 27, 2025|website=Reaper Feed}}

On July 12, 2006, the magazine Mother Jones provided excerpts from the transcripts of a selection of the Guantanamo detainees.

The article informed readers:

{{quote|More than a dozen detainees were cited for owning cheap digital watches, particularly "the infamous Casio watch of the type used by Al Qaeda members for bomb detonators".}}

The article quoted Guantanamo Bay detainee Abdullah Kamel Abdullah Kamel Al Kandari:

{{quote|When they told me that Casios were used by Al Qaeda and the watch was for explosives, I was shocked ... If I had known that, I would have thrown it away. I'm not stupid. We have four chaplains [at Guantanamo]; all of them wear this watch.}}

• Chung Eui-sun{{Cite web|date=May 15, 2019|title=Rich and Powerful Men Who Wear Casio Watches - G-Central G-Shock Fan Site|url=https://www.g-central.com/rich-and-powerful-men-who-wear-casio-watches/|access-date=February 26, 2025|language=en-US}}
• Barack Obama{{Cite web|last=Casio-Admin|date=October 10, 2024|title=Famous People Wearing Casio Watches - Casio Centre Pakistan|url=https://ecasiocentre.pk/famous-people-wearing-casio-watches/|access-date=February 26, 2025|language=en-US}}
• Osama bin Laden
• Chuck Feeney
• Subcomandante Marcos{{Cite web|date=May 11, 2022|title=How The Casio F91W Became The Worlds Most Dangerous Watch {{!}} The Gear Bunker|url=https://www.thegearbunker.com/how-the-casio-f91w-became-the-worlds-most-dangerous-watch/|access-date=February 26, 2025|language=en-US}}
• Adam Driver as Jamie in While we're Young. I dont know how to cite. https://www.pinterest.com/pin/the-casio-edifice-mens-watch-of-jamie-adam-driver-in-while-were-young-the-casioedifice-mens-watch-of-jamie--668151294709991567/ but here is a picture

File:Casio F-91 Module 593 Displaying CASIo.jpg

Counterfeits of this watch are very common, despite its low price tag. These counterfeits generally have a lower plastic build quality, narrower LCD viewing angles, louder and higher-pitched beeps, and significantly less accurate timekeeping than genuine models.{{cite web|date=July 2018|title=Comparing a genuine Casio F91-W with a fake|url=https://www.burningimage.net/genuine-and-fake-casio-f91w/|url-status=live|archive-url=https://archive.today/20250127203119/https://www.burningimage.net/genuine-and-fake-casio-f91w/|archive-date=January 27, 2025|access-date=January 27, 2025}} The newer modules with the green LED light can be tested by holding the right button for over 3 seconds in the main timekeeping mode; this will lead the display to show "CASIo", as a test for authenticity. With the advancement in technology, however, some counterfeit models have also been developed to show this sign. This leaves the only method of distinguishing them as assessing the overall build quality, timekeeping accuracy, display viewing angle and the printing on the screen glass.{{cite web|last1=Nguyen|first1=Khoi|date=August 31, 2018|title=Casio F91W Review - Retro Digital Sport Watch|url=https://www.gentlemanwithin.com/casio-f91w-review/|url-status=live|archive-url=https://archive.today/20250127202818/https://www.gentlemanwithin.com/casio-f91w-review/|archive-date=January 27, 2025|access-date=January 27, 2025|work=Gentleman Within|language=en|type=review}}

{{clr}}

{{Reflist}}

• {{commons category-inline|Casio F-91W}}
• [https://www.casio.com/products/watches/classic/f91w-1 F91W-1 product page], Casio website

{{Casio}}

{{DEFAULTSORT:Casio F91w}}

F91W

Category:Products introduced in 1989