Casio F 91w

• Casio F 91w Terrorist
• Casio F-91w Manual
• Casio F-91w How To Change Time
• Casio F 91w Reviews

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]

Release date controversy[edit]

1. Product: Casio F-91W-1Q(D002) Vintage. Review by THEJASWI GOWDA A on 11th May, 2019 Verified Purchase Product is good, awesome and worthy for money. But its took more than 72 hours to deliver the product. Was this review helpful to you? 1 of 2 people found the following review helpful.
2. The Casio F-91W is one of the most iconic watches of the past few decades. It’s notoriously cheap, reliable, and retro; in fact, it’s probably the only watch that was worn by both Obama and Osama. At just under $10, it’s the perfect daily beater watch.
3. The latest WikiLeaks dump has revealed that a disproportionate number of terrorism suspects in America's most notorious prison were apprehended wearing a Casio F-91W, a plastic digital watch you.
4. The Casio F-91W measures 37.5mm by 33.5mm by 8.5mm and weighs only 85g, according to Wikipedia — and not every watch model out there has its own Wikipedia entry, further speaking to the F-91W’s specialness. This is an extremely comfortable watch to wear that simply and unobtrusively does its job well.

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.

Casio F91W 1SDG product offers from exporters, manufacturers, suppliers, wholesalers and distributors globally by price, quantity, order, delivery and shipping terms, country - Page 1.

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.

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:

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 F 91w Terrorist

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

The Casio F-91W is one of the most iconic watches of the past few decades. It’s notoriously cheap, reliable, and retro; in fact, it’s probably the only watch that was worn by both ObamaandOsama. At just under $10, it’s the perfect daily beater watch. And in the age where you need to charge your Apple Watch every day, the Casio’s battery can last up to a decade. Still, though, it has a few downsides:

• The resin strap is liable to break
• The watch is barely water resistant

The former is easily rectified by switching to a vinyl or leather NATO strap; but what about the latter? Is there any way to turn the F-91W into a deep sea diver?

The Magic of Fluid Incompressibility

Fluids are said to be “virtually incompressible.” Generally speaking, a gas (like air) is compressible: when pressure increases, volume decreases. The compressibility factor (beta) may be expressed as

$$beta = -frac{1}{V}frac{partial V}{partial p}$$

where (V) is volume and (p) is pressure. A trick to achieve incredible depth ratings has been to submerge the internals of a watch in inert, non-reactive, non-corrosive, non-polar liquids. Mineral oil (a byproduct of petroleum refinement) is a fantastic choice — and this is exactly what I’ll be doing to my Casio F-91W. Theoretically, as water pressure increases around the watch, due to the fact that it’s filled with an incompressible liquid (as opposed to a compressible gas), it can successfully “push back” against the water and it will not succumb to implosion due to increasing pressures.

Step 1: Preparing the watch

First, we take off the stock resin straps and wipe off the watch of excess oils and debris.

Step 2: Unscrew the back plate

We next unscrew the back plate and remove the watch internals, also removing the white tape on the back of the battery compartment. All parts are wiped carefully with with rubbing alcohol.

Step 3: Fill bowl with mineral oil

Some sources suggest heating the mineral oil to ~50° Centigrade, but I’m not exactly sure what the reasoning for that might be, so I stuck with room temperature. For some extra flair, I added a fat-soluble colorant which will give the viewport a nice bluish tint and set it apart from a stock F-91W.

Step 4: Submerge

Slowly submerge all watch parts in the mineral oil. Ensure that there are no air bubbles in either the watch chassis or electronic internals. Leave watch submerged while mixing slowly for a few minutes to make sure there are no air bubbles.

Casio F-91w Manual

Step 5: Re-assemble the watch

Re-assemble the watch by securing the back-plate via the Phillips screws while submerged in the oil. Make sure no air bubbles accidentally form while screwing in the screws.

Casio F-91w How To Change Time

Here, you’ll notice I decided to switch to a reddish tint after my first failed attempt.

Step 6: Extract watch and clean

Remove the assembled watch from the oil mixture and wipe it down, cleaning any excess oil. Add a fancy strap, and et voila!

Final Words

Casio F 91w Reviews

If you decide to use colorant, as I did, keep in mind this will effectively reduce visibility to zero and it will be very difficult (but not impossible) navigating the murky oil solution by touch alone. Also, keep in mind that after this procedure the F-91W’s nigh-useless LED light will be even more useless due to the oil’s refractive index. Finally, even though mineral oil is “virtually incompressible,” it’s still technically compressible. Professional dive watches filled with oil will often have a flexible chassis that will allow for around a (pm0.5%/1000text{psi}) wiggle room in volume to account for this compression at high ambient pressures.

So what kind of pressure can my little Casio handle? I don’t have any way of testing, but a similar experiment (on a Casio G-Shock) allowed for pressures of up to 1200PSI, so I would expect similar numbers out of my watch. Another enthusiast did this experiment on an F-91W with olive oil. However, olive oil will oxidize, so if you’ll give this a try, I would suggest a synthetic compound.

Overall, this was a fun little project and not a bad way to spend a lazy Sunday.