Casio F-91W
The Casio F-91W is a digital watch manufactured by Japanese electronics company Casio. Introduced in June 1989 as a successor of the F-87W, it is popular for its low price, long battery life, and iconic design. As of 2011, annual production of the watch is 3 million units, which makes it the most sold watch in the world.
Specifications
Design
Designed by Ryūsuke Moriai as his first design for Casio, the case of the F-91W measures. The case is primarily made of resin, with a stainless steel caseback and buttons, with the manufacturer's module number, 593, stamped on the caseback. The resin strap is at the fitting and 22 mm across the widest part of the lugs. The total weight is.Features
The F-91W has a chronograph, featuring precision of seconds with a count up to 59:59.99. The chronograph is also able to mark net and split times. 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. The watch uses a faint green LED backlight located at the left of the display for illumination. 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.
Water resistance
The front of the watch is marked "Water Resist". The black version is "30 meter / 3 bar", 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
The watch is controlled by three side-mounted push-buttons.- The upper left button, labeled "Light" and designated as "L" in the manual, activates the backlight, cancels the alarm, resets the stopwatch or records a split time, and is used to navigate settings.
- The lower left button, labeled "Mode" and designated as "C," cycles the modes: time display, alarm, stopwatch, and time/date adjustment.
- The right button, labeled "Alarm On-Off/24hr" and designated as "A," serves as the primary function button: it starts and stops the stopwatch, changes the setting currently being adjusted, or switches between the 12- and 24-hour configurations. These actions depend on what mode the watch is currently in.
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 – at all times, the alarm signal status, and the hourly signal status are present when activated in the alarm mode.
In stopwatch mode, minutes, seconds and hundredths of a second are shown.
Usage in terrorism
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.According to secret documents issued to interrogators at Guantanamo Bay, obtained 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." United States military intelligence officials have identified the F-91W as a watch that terrorists use in constructing time bombs.
This association was highlighted in the Denbeaux study, and may have been used in some cases at Guantanamo Bay. 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. Casio watches were mentioned almost 150 times in prisoner assessments from Guantanamo.
On 12 July 2006, the magazine Mother Jones provided excerpts from the transcripts of a selection of the Guantanamo detainees. The article informed readers:
The article quoted Guantanamo Bay detainee Abdullah Kamel Abdullah Kamel Al Kandari:
Variants
| Model name | Description |
| F-91W-1xx | Essentially the standard black F-91W-1 model with minor regional differences, usually to do with packaging.
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| F-91W-3, F-91WG-9 | Similar to the original F-91W, but including a green and gold trim respectively on the face. Gold variant has gold colored function buttons |
| F-91-WB series | Simplified case print, print on face and strap: blue-gray on black, bronze on black, white on blue, gray on white. |
| F-91-WC series | Neon colors for case, face and strap: orange, blue, green, pink, beige and yellow. |
| F-91-WM series | Metallic colored cases with black straps: grey, army green, blue, silver and gold. |
| F-91-WS series | Translucent straps with muted case colors: blue, pink, white, and grey |
| F-84W | Japanese Domestic Market model. Uses the same 593 module, but the case design is more similar to the older F-28W and F-87W. It has lugs instead of an embedded strap. |
| F-94W | Circular icon arrangement in the display. |
| W-59 | Black case with rounded corners and blue accents on the face. Waterproof up to 50 meters. |
| A158W, A159W, A163W, A164W | Chrome plated case, stainless steel band. |
| A159WGEA-1 | Ion plated gold stainless steel band, gold colored chrome plated case. |
| F-105W, A168W, A168WG, A168WEGM, A168WEM, W-86 | Equipped with electroluminescent backlighting instead of the LED backlight in the other variants. Available in black with a resin strap or in silver or gold colors with a stainless steel bracelet. Slightly different icon arrangement on the display and a thicker case due to the backlight system. Some versions also feature a negative display. |
| LA680 | A smaller variant, marketed towards women |