1. Casio Quartz Watch
2. Casio Quartz Diver
3. Casio Quartz Alarm Chronograph 100m
4. Casio Quartz Watch
5. Casio Quartz Alarm Clock

The Casio F-91W is a digital watch manufactured by Japanese electronics company Casio. Introduced in 1989^[1] and modeled after the 1984 model DW-240, it is popular for its low price and long battery life.^[2] Annual production of the watch is 3 million units.^[3]

History[edit]

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• Casio Men's G-Shock Quartz Watch with Resin Strap, Black, 20 (Model: DW5600E-1V) Imported With its high-tech functions, shock resistance, and comfortable resin strap, this Casio watch is a reliable go-to timepiece.
• CASIO Mini Card. First card-sized calculator (3.9 mm thick) Sep. First wristwatch equipped with CASIO LCD. Sigma-8700 series.
• (199) 199 product ratings - Casio Men's Quartz Rotating Bezel Black Resin Band 45mm Watch MRW200H-1BV. Casio Men's Quartz World Time Gold & Black Resin 50mm Watch AEQ110BW-9AV. 5 out of 5 stars (1) 1 product ratings - Casio Men's Quartz.

Release date controversy[edit]

The Wikipedia article for the F-91W watch has gained attention from KSNV for an incorrect release year being propagated in the article by circular reporting. The article, since March 2009, reported an incorrect release year of 1991, which was repeated in a BBC article suspected of sourcing the date from Wikipedia. The BBC article was then cited as a source for the 1991 release year. Personal communications with primary sources repeatedly affirmed a release year of 1989, but a dismissal of the communications as proscribed original research in favor of the BBC citation led to the false release year remaining.^[1] The false release year was corrected in 2019, citing KSNV's article about the controversy as a source.

Specifications[edit]

Design[edit]

Designed by Ryusuke Moriai as his first design for Casio,^[4] the case of the F-91W measures 37.5 by 33.5 by 8.5 millimetres (1.48 by 1.32 by 0.33 in) and weighs 21 grams (0.74 oz). The case is primarily made of plastic, with a stainless steel caseback and buttons with the manufacturer's module number, 593, stamped on the caseback. The resin strap is 18 millimetres (0.71 in) at the fitting and 22mm across the widest part of the lugs.

Features[edit]

The F-91W is a chronograph, featuring a ​¹⁄₁₀₀ second stopwatch with a count up to 59:59.99 (nearly one hour). The stopwatch also has the feature to mark net and split time (lap). Other features include an hourly time beep and a single daily alarm lasting 20 seconds and an annual calendar, with adjustment for leap years not supported as the watch does not record the year. February is always counted as 28 days.^[5] The watch uses a faint, green LED backlight located to the left of the display for illumination (in earlier versions it was an amber microlight). According to manufacturer estimates, the watch is reported to be accurate to ±30 seconds per month.^[5]

The quartzmovement, designated Module 593, is powered by a single CR2016 3-volt lithium button cell.

Water resistance[edit]

The watch front is marked 'Water Resist',^[5] but Casio reports different values for different variants of the watch. The black version (F91W-1)^[6] 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'.

Operation[edit]

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. Pressing all three buttons at the same time will fill all the cells on the LCD until any button is pressed again.^[7]

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.

Casio Quartz Watch

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

Usage in terrorism[edit]

According to secret documents issued to interrogators at Guantanamo Bay, obtained^[8] 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.'^[9] United States Military intelligence officials have identified the F-91W as a watch that terrorists use in constructing time bombs.^{[10][11][12][13]}

This association was highlighted in the Denbeaux study, and may have been used in some cases at the Guantanamo Bay detention camp.^[14] 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.^[15] Casio watches were mentioned almost 150 times in prisoner assessments from Guantanamo.^[16]

On July 12, 2006, the magazine Mother Jones provided excerpts from the transcripts of a selection of the Guantanamo detainees.^[12]The article informed readers:

Casio Quartz Diver

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 Abdullah Kamel Abudallah Kamel:

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.

Variants[edit]

Casio Quartz Alarm Chronograph 100m

Counterfeits[edit]

Counterfeits of this watch are very common, despite its low price tag. These counterfeits generally have a lower plastic build quality, the LCD viewing angles are not as wide, the beeps are louder and higher-pitched, and are significantly less accurate than the original.^[19] 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, although these are fairly uncommon. 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.^[19][20]

References[edit]

1. ^ ^abcMoyer, Phillip (June 15, 2019). 'The case of an iconic watch: how lazy writers and Wikipedia create and spread fake 'facts''. KSNV. Retrieved June 19, 2019.
2. ^'Casio F91W-1: The retro watch with a strange double life'. Montredo. February 4, 2020. Retrieved April 19, 2020.
3. ^'Casio F-91W – the classic quartz digital watch'. ICON. Retrieved August 6, 2019.
4. ^Ariel Adams (April 16, 2017). 'An Afternoon In Tokyo With The Man Who Designs Casio G-Shock Watches'. [A Blog To Watch. Retrieved July 6, 2019.
5. ^ ^abc'F91W-1 Classic Timepiece'. Casio. Retrieved April 27, 2011.
6. ^'F-91W-1XY'. Casio. Retrieved May 22, 2013.
7. ^'Manual'(PDF). Casio. Retrieved November 26, 2014.
8. ^'Guantánamo files: How interrogators were told to spot al-Qaida and Taliban members'. the Guardian. April 25, 2011. Retrieved April 10, 2019.
9. ^James Ball (April 25, 2011). 'Guantánamo Bay files: Casio wristwatch 'the sign of al-Qaida''. The Guardian. London.
10. ^'USA v. al Qahtani'(PDF). US Department of Defense. November 7, 2005. Retrieved February 27, 2007.
11. ^'Combatant status review board for Mohammed Ahmad Said el Edah'. The New York Times. October 6, 2004.
12. ^ ^ab'Why Am I in Cuba?'. Mother Jones. July 12, 2006.
13. ^'Summary of Evidence memo (.pdf) prepared for Sabri Mohammed Ebrahim Al Qurashi's Combatant Status Review Tribunal – page 216'(PDF). October 13, 2004. Archived from the original(PDF) on July 31, 2006.
14. ^'Empty Evidence'. National Journal. February 3, 2006. Archived from the original on July 4, 2008.
15. ^R. Jeffrey Smith (July 21, 1996). 'New Devices May Foil Airline Security'. The Washington Post. pp. A01. Retrieved March 14, 2008.
16. ^Batya (July 9, 2020). 'How did the Casio F91W Become a Terrorist Icon?'. Reaper Feed.
17. ^'Casio Collection Timepieces Products CASIO'. www.casio.co.uk. Retrieved June 8, 2019.
18. ^'Casio International Timepieces Digital F-91WS-2 CASIO'. www.casio-intl.com. Retrieved April 8, 2020.
19. ^ ^ab'Comparing a genuine Casio F91-W with a fake'. July 2018. Retrieved March 25, 2019.
20. ^Nguyen, Khoi (August 31, 2018). 'Casio F91W Review - Retro Digital Sport Watch'. Gentleman Within (review). Retrieved August 28, 2019.

External links[edit]

• Media related to Casio F-91W at Wikimedia Commons
• F91W-1 product page, Casio website

Casio Quartz Watch

Casio Quartz Alarm Clock