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the watch pictured in head of article is not F91w.
It definitely is in the family. I say this while staring at my stack of F91W-1 Classics. The only difference between mine and the one in their header is the top right says “ALARM” instead of “F-91W”, and a few other minor face label differences. Unless it’s a counterfeit, but either way every other detail looks spot on.
it looks like casio w217h
I think you are correct. I didn't realize they would look so similar.
Looks at my wrist

Uh oh...

Or maybe because it’s a $6 watch...

Kinda like how 90% of murderers have been shown to eat bread within 12 hours of their killing.

Heh, next up could be a story about the AK-47 rifle using the same premise.
The article talks at length about the fact that both the F91W and the AK-47 are excellent, sturdy low cost devices, that are therefore widespread both among terrorists and non terrorists.
Good catch, did not see that initially in the article.
I wrote about the F-91W last year in a post[1] that went viral-ish. Interestingly, it's probably the only article of clothing worn by both Obama[2], and Osama[3]. I wouldn't go as far as calling it a "terrorist icon" -- it just happens to be literally the cheapest mass-produced digital watch ever made. It's very sturdy, relatively waterproof, the battery should last around a decade, and it even has a (terrible) LED for low light conditions!

I started getting into watches last year, and the F-91W is a sort of rite of passage in watch circles. I've since bought a few expensive† ($1000+) watches for my collection, but I often find myself wearing the Casio. Yeah, I modded it and it has a bit of personal attachment, but it's not just that. There's something really strange about it: it fits so snugly on my wrist, so warm, yet spartan; it simply just feels good.

[1] https://dvt.name/2019/06/03/hacking-the-casio-f-91w-to-handl...

[2] https://static.highsnobiety.com/thumbor/hC8faiWSsiFpNpszRf0l...

[3] http://ethiopiaforums.com/wp-content/uploads/2010/05/osama-b...

† This is of course relative. Watches can cost up to millions, and serious watch collectors have watches that can easily go up to $50,000++.

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What mods did you make to your Casio?
I filled it with mineral oil and gave it a NATO strap, see my first link!
Very cool idea. Haven't had any leakage issues since doing it?
Nope! I was a bit worried about flying with it, but no leaks there either.
I'm a bit of a Casio watch collector; I think the count is currently about 10. Three of them are variations on the F91W, including the metal-banded A158W. I also have several MQ24's (analog face, ~$10). There's an F91W that has a "gold" case too, for just a couple dollars more.

If you watch Napoleon Dynamite closely, you'll note that Napoleon has an F91W, but his "classy" uncle has an A158W. It was funny to someone like me.

> If you watch Napoleon Dynamite closely, you'll note that Napoleon has an F91W, but his "classy" uncle has an A158W. It was funny to someone like me.

Hah, I definitely missed this detail, I must've last seen Napoleon Dynamite years ago.

Terrible LED? I thought that blue illuminator was super cool. And it was actually an EL film, not an LED.
I think you're thinking of a different watch. The F-91W has a green LED[1] that's notoriously terrible (not to mention lopsided).

[1] https://www.instructables.com/id/Watch-LED-Light-Mod/

Ah yes indeed, I had the F-105W. I thought the F-91W also had this EL film, because it's also labeled "Illuminator" on the big picture at the top of the article, which was casio's branding for this technology at the time. But it doesn't have the blue branding. And I think that pic at the top isn't actually an F-91W.

The EL light was super, very bright and very well distributed (because the whole backlight film would light up). I'm surprised they managed to put one in such a small watch as EL film needs fairly high voltages, you could hear the switching coil whine when it was on :P Yet it still lasted a good while on battery.

The F105W is what you graduate to after you realize the F-91W is essentially useless is the dark. I've worn both since the early 90s. The band always breaks before the battery or watch itself dies, but i still get a few years before the band breaks.
The somewhat more complicated and modern Casio watch I had also had this EL whine. Now I finally found out why it occurs, so thanks for that! The silent F-91W was almost pleasant in comparison despite its uneven and (IMO) not very pretty lighting.
Just wanted to say that I read your blog post when it first went around last year, and it made me fall in love with the look and the idea of the f91w. Currently have three, all found in thrift stores. They are functional, aesthetically pleasing, and such an affordable collectable. So, thanks! :)
Thanks and that's awesome, enjoy your collection!
Claude Shannon defined information in part by its ability to distinguish from noise.

Certain objects are so ubiquitous and their signaling so minimal, it’s to the point of background noise and contextlessness.

The Casio F-91W is one such object.

The monobloc chair is another[1].

The community jokes a CIA analyst looking at a gritty Polaroid of a monobloc will have no ability to discern if the picture was taken in Djibouti or Denmark.

In a certain, Cayce Pollard / William Gibson “CPU” aesthetic, there is cachet and delight in signalling contextlessness - and a small cult has grown around these objects. They collectively call objects that share this anonymous property “monoblocs“ for short and their is a bit of fun in acquiring the most base form (counter to our every instinct!)

I liked your article’s tangent on incompressibility. As, like fluid, noise is incompressible and by reinforcing your F-91W, you have made it doubly so.

[1] http://www.ethanzuckerman.com/blog/2011/04/06/those-white-pl...

This is an awesome comment, thank you!

I had no idea of this new "monobloc" trend, but I feel like you're on to something. When I wear, say, my Longines Diver and I look at my wrist, I feel that my watch is communicating: it's an intricate, hand-built machine telling me the time. I need to wind it and breathe new life into it. I get complimented on it: "new watch?" or "nice watch, what is it?" It's an accessory. A deliberate choice.

When I look down at my F-91W, it's as if it's not even there. I'm the one telling the time. Everyone ignores it, no one mentions it, no one brings it up: it's there but it's not. Just like a monobloc chair or a #2 pencil.

There is a YouTube channel called Bryan Ropar's Plastic Chair World[0]. Bryan is an expert when it comes to these monobloc chairs, and can name every model by sight and tell you where it was produced.

I think we often underestimate how much depth there is to subjects we are only casually familiar with, and I'm sure a CIA analyst could glean a great deal of information from a still of a plastic chair.

[0]: https://youtu.be/yCotpBAqJho

I LOVE Bryan Ropar's Plastic Chair World. I never thought I'd see it called out on hackernews!
New fan here. I'm always really happy to see real people with real niche interests publishing online, in a totally non-commercial context.
That's the kind of video countdown I like: quick and over in less than two minutes. No long, overdrawn filler in between each item.

At the same time, I'd like to see an article that explains why he considers one plastic chair superior to a different one, or what was the basis for ranking the chairs in the order he did.

I've been trying to refind this channel for years. Thank you.
Great comment and a great link. One question - what do you mean by "Cayce Pollard / William Gibson “CPU” aesthetic" They're both cyberpunk authors, yes?
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Cayce is a Gibson Character. Part of the characters thing is not wearing any clothing that has branded logos, amongst other constraints.
Not the OP, but Cayce Pollard is the main character from Gibson’s Book “Pattern Recognition”. In the book, there is a subculture obsessed with a movie that has been deliberately distributed in small pieces. The fans try to discern the meaning of the movie and are foiled in determining the year or location it was shot due to the deliberate generic-ness of the costumes.

I don’t know what CPU aesthetic is, though.

"CPU" is a "Cayce Pollard Unit", an outfit she wears that is effortlessly cool and blends into the background, consisting of black, grey, and white.
Akshually, a CPU is an individual component of an outfit, eg. a black fruit of the loom t-shirt with the labels cut out.
Thank you for the comment.

>>In a certain, Cayce Pollard / William Gibson “CPU” aesthetic, there is cachet and delight in signalling contextlessness - and a small cult has grown around these objects. They collectively call objects that share this anonymous property “monoblocs“ for short

Do you have more information on this ? Searching for monoblocs doesn't turn up anything useful apart from the monobloc chair.

I don't know the specific community that uses that term, but more generally it has some things in common with "gray man", but Gibson filters it through fashion and otaku lenses.
Have you tried to buy a Monobloc chair? A quick web search only reveals clones rather than the classic original. The original is so ubiquitous that it is near impossible to buy. I would want one rather than a generic plastic chair because it is iconic much like the Casio F-91W, but, thus far, I haven't been able to find one (or four) to buy.
>> The monobloc chair is another[1].

I hate this chair with a passion. Didn't even know it had a name.

I also have a few expensive watches and the F-91W is my go to watch where I don't care about breaking it. It has been through bike crashes, slapped on the sides of water slides and all kinds of abuse. Its just a great product for some use cases.
I was inspired to replicate your hack for myself. It was a fun afternoon, and that watch keeps going (though I had to carve away plastic to get the band on). Thanks!
> There's something really strange about it: it fits so snugly on my wrist, so warm, yet spartan; it simply just feels good.

Totally agree. And it's great utility because of this. You can use it while playing, sports, music and it doesn't get in the way. There's no anxiety of busting and if you do it's cheap to replace.

This is exactly why I love the simple Casio designs too. The F91W is so light and simple, and I have ZERO fear of washing my hands with it or bashing it in to the wall while pulling cables. I usually forego the F91W for something like the WS1200 or the SPH-600, usually about double the price of the F91W but with a bunch more features AND still not scary to wear in any situation.
I hate the buttons on that watch. They are prominent enough to always get stuck with whatever I slip my arm through. Especially backpack straps.

Otherwise love it. The battery lasts longer than the plastics. Has this timeless 80s chic of the original Walkman and Thinkpads.

I would love the calculator one more, but that is critically missing a light, which makes it impractical.

Pretty sure my Casio calculator watch has a light since I remember using it. If I could just remember where I stashed it...
I've always been fascinated by mechanical things, steam-engines, analog watches, analog clocks, etc. (I've a few of each).

The only digital watch I own is the F-91W, and I think it makes a nice contrast between the watches I wear more regularly.

I enjoyed your blog post, that's an interesting mod.

> 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.

I expect this is just to reduce the viscosity of the oil so that it fills the cracks more easily.

Oddly enough the Casio classics are starting to have quite a premium here due to the retro look. I've seen as capable digital watches at 1/3rd the price at the local Decathlon. Casio is milking their legacy quite a bit.
Ha, still have my casio watch calculator from the 80's

Guess I should see if the battery has exploded and if not get it out of there :/

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Also a big fan of modding F91W's and other Casio's. My favorite is the Casio FE10-1A which doesn't look as good but whose face shows the numbers more clearly at a variety of angles and lighting conditions.

I like to replace the watch bands with a pair of elastic hairbands. It makes the watches much lighter and more comfortable in a variety of scenarios:

- Running (doesn't bounce around or get sweaty)

- Yoga/pushups (can bend wrist fully)

- Typing on a laptop (wristband doesn't hit the edge)

I do have to change out the elastic hairbands every 4 months or so as they stretch out, and there's about a week of breaking it in where the new bands are too tight. Otherwise it's so great I'd seek to commercialize it.

Photos: https://imgur.com/a/qNJ4MuG

If anyone wants to try it out and could use some tips let me know.

Modding the F91W was a nice Corona project that I did with my kids. Inverting the display, changing the led and inserting an nfc chip. Not too difficult, but it gives you something unique(ish) that is actually useful.
Thank you for that post last year! It inspired my friend and I to spend a day having fun modding a few we picked up. Still no water intrusion after over a year of near-daily wear...
>I wouldn't go as far as calling it a "terrorist icon" -- it just happens to be literally the cheapest mass-produced digital watch ever made. It's very sturdy, relatively waterproof, the battery should last around a decade, and it even has a (terrible) LED for low light conditions!

Yes, the article even points out four chaplains also wore it. "Cheap, reliable and common watch is also popular with terrorists" isn't as sexy a headline though.

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I would have thought my GW-M5610-1ER would be the better watch, with GShock and solar (Love the watch). But perhaps too expensive.
I have a GW-500A myself (G-Shock, solar, radio clock). It is my favourite watch but I wish it weren't as bulky/a bit heavy as it is.
I feel like the GW-M5610-1ER is smaller, try out one once.
While certainly not as cheap, the Casio Wave Ceptor watches have great utility. My favorite travel watch is the WVA-M640-1AJF. It is always accurate, always charged, and allows me to quickly see what time it is in another time zone. Before I bought it, I forgot that there were watches focused on function over form. Don't get me wrong, I love a good looking watch, but sometimes you want a tool over an art piece.
If you like the F91w but want something beefier, the DW5600 has the cachet of being rated space-worthy by NASA and looks similar but bigger. Costs about $50, not $12 though.
Wouldn't the next logical choice on the "beefiness scale" be a G-Shock? (Personally I can recommend the GAW-100B-1AER for about $100)
I have had GW-M5600 for years. It has all you need from a watch and nothing more. It's almost perfect watch.

1. It's small and looks like G-shock classic and has typical C-shock features.

2. Solar powered.

3. Multi-band 5 timekeeping from atomic clocks in the US, EU or Japan. I set the time once after I bought it and just switch daylight savings time twice a year.

The only issue is that it needs integrated strap specific to the model, not generic one. Casio straps for G-shocks break in everyday use in every 5-6 years. Durable stainless steel strap costs $100, roughly the same as the watch itself.

This is my go-to everyday watch. Have had it for over 10 years and it never skipped a beat. I've had dozens of watches cycling through my collection throughout the years, GW-M5600 has been the only one that I'd never considered letting go of. When the straps break, I'll just go with a good black Nato strap. If I had somehow lost this watch, I'd buy another one without hesitation.

My only real complaint is the countdown timer is only 1 hour. There are times I could use a 24-hour countdown timer.

A minor nitpick is the watch's thickness is just a tad too think to be worn under shirt cuffs. If Casio would ever release a 25-30% thinner version with the same features, I'd buy it in a heartbeat.

I’d love to get more G-Shocks in this [style](https://g-shock.jp/products/origin/gmw-b5000/) but they are too damn expensive. $100 is my range for a watch but some of these are $500+!

I don’t know why Casio charges so much. I’d think that if they reduced the price then people would buy more.

The other annoying thing about G-Shocks is the band. I have a all-black model with a clasp link band. I love it. It’s super easy to remove and put back on when I’m using they keyboard.

they are solar, stainless steel, with no moving parts. which means they are practically indestructible without any need for maintenance. that's why they are sold at that price point
There are kits on Aliexpress/Taobao (I'm guessing Amazon as well) where you can convert any 5600/5610 to a metal bracelet. It has the casio and g-shock branding, so you have to be OK with a bit of light piracy. =) I did it last year and the version I got was really high quality. The buttons are a bit small on 5600/5610 though, so they are a bit harder to press.
this seems like one of those things where it's just ubiquitous, so of course Terrorists would use it. like Toyota trucks [1]

[1] https://medium.com/war-is-boring/the-toyota-pickup-truck-is-...

Does owning one of those trucks get you in trouble?

I still miss the Wikipedia article "List of Guantanamo Bay captives accused of possessing Casio watches" (I think republished at http://wikialpha.org/wiki/List_of_Guantanamo_Bay_captives_ac... ) which seemed to give evidence that watch ownership was used to classify people in detention camps.

That point is mentioned in the article, including the example of Toyota trucks
I generally try and buy counterfeit stuff, that's my thing.

But I have never checked my Casio F91W is counterfeit, so I figured it's a good time, I used this -

https://www.youtube.com/watch?v=pGuJAJ0I1Cg

My watch says made in Japan, so I guess it's a genuine fake. But it is full of water, so that bit sucks.

I can understand countefeit Rolexes, Breitling, etc...but why would you bother to buy a counterfeit of a $15 watch?

EDIT: that video is fascinating. The different in beep frequency is a dead give-away, though.

If it costs 2-3USD to make and you can sell a million worldwide... :)
I needed a watch while travelling in Vietnam and bought an F91W from a market stall for a few bucks. It's such a cheap watch I didn't even consider that people sold fakes.

A few weeks later I noticed it was slowly losing time and had some other issues, clearly a fake or reject watch. So that's how, I guess.

nobody bothers to buy it, sellers just get a better margin.
Wow, I lovvvee this. I just checked my three casios, and one does say made in japan on it, so that suggests fake - but everything else seems legit (logo printing, display evenness, hidden button functions, beep-tone), so it's either a better fake than in that video, or some of them are in fact made in japan.
At some point I think they were IIRC but not in (relatively) recent history
The 'beep' is the dead give-away on non-Casio Casios. I have a handful of replica G-Shocks, Frogman, Gravitymaster, etc. and the beep frequency is wrong even when the more advanced features like compass and thermometer work. For what its worth, they cost about 1/10th their genuine counterparts and are visibly identical.

One last word of caution, even the F91W fakes do the three-button CASIo module thing now.

Uh oh...

I had one of these when I was young (though it may have been the pretty similar F-105W actually). I loved that cool blue glow. In fact I think the only difference between the F-91W and F-105W was the print on the front.

Edit: Nope, the F-91W had a poor green LED, the F-105W had super cool blue electroluminescent backlight, so that was the difference, thanks to dvt for pointing this out.

Also, I have a satellite phone, and many radio transceivers (mentioned in the article). Just the "Large quantities of cash" I don't have (I buy too many radios and other toys lol).. I suppose I'm on a list now :D

When my F-91W breaks I will upgrade to a F-105W.
don't hold your breath
The watch never breaks, but the strap will break after 1-2 years of continuous wear, and its cheaper to get a whole new watch than a new strap.
Is it just me or is this short on details? I don't see any reason this timer is actually easy to wire up, and I remember my similar watch decades ago also as being water resistant, so it seems like it's less than ideal?
Well, maybe it's not so easy to wire, but if you want to make an accessible bomb-making tutorial, you have to use materials that are easily obtainable...
whilst going into dubious territory, i also wondered the same. I assume its something to do with the speaker only being used for alarm bleeps?

from what i remember from failed watch repairs on these as a child, there's really nothing super easy about that connection

I think you just hook up a relay/transistor to the the small piezo buzzer that make noise for the alarm. Its dirt cheap and very easy to come by, so I guess that is why it as been used in bomb timer making.
The back case is actually the piezo speaker, and it connects with springy contacts not a soldered or wired connection. I would imagine this opens up a variety of easy ways to connect this to a relay for a "louder" alarm.
When I was doing my conscription military service (I am Swedish) I noticed how hard it was to tell time in the darkness of the night with my existing analog watch.

So I asked my parents for a cheap digital watch with inbuilt light. I got something similar to this Casio but am not sure if it was exactly this. But the darkness readability aspect of a watch had never been a concern for me prior, or after, but during that year the most important feature. Perhaps terrorists operating in the dark as well have come to a similar conclusion.

I noticed how hard it was to tell time in the darkness of the night with my existing analog watch.

An analogue watch with SuperLumiNova(tm) will be usable all night from a 10 second blast with a good torch. Source: regularly do this.

Torch as in flashlight, for us north americans.
10 second blast with an oxy-acetylene torch and it'll be illuminated for the rest of its useful life.
The F105-W is what you graduate to after you realize the F-91W is essentially useless is the dark. I've worn both since the early 90s. The band always breaks before the battery or watch itself dies. But i still get years out of them.
I wear a similar Casio and this article reads like "How did breathing oxygen become a terrorist icon". I mean come on, it's one of the most common watches on the planet. The best correlation the article could come up with is that 1/3rd of people caught with it also had bombs. That's worse than random chance.
That's only worse than random chance if the base rate of having bombs (among people ending up in Guantanamo Bay, anyway) is more than 1/3. Were you assuming it would be 1/2 or something? I don't see any reason to conclude that. I can easily believe that the base rate would be under 1/3, and so 1/3 would in fact be better than random chance.
I've bought a bunch of these to give away to newly elected patrol leaders in our boy scout troop because they are cheap and get the job done... the job being to tell time. I wonder if that means I'm on a list now.
I loved my F91W when I was in school. I recently bought one again just because it was so dirt cheap! It's an excellent watch. Does everything you expect a watch to do, and does it well.
They are also pretty popular in the British army because they are, in many ways, the best watch available.

That said, they have a few limitations:

* The backlight is pretty weak

* The stopwatch tops out at 1 hour

* It needs batteries, as opposed to solar or kinetic charging (this is probably why the backlight is underpowered)

* It would be great if it had a compass.

> The backlight is pretty weak

The reason for this is because the LED is mounted facing directly up, not facing the display. I've seen some mods where they replace the LED with a side-facing and it's far better.

They are also pretty popular in the British army

Casio do a British Army G-shock now but I can’t imagine any actual soldier using it, it’s 2cm or more high and has features that will snag on anything. The F91w is very thin. It’s more marketed towards airsofters I reckon.

https://g-shock.co.uk/mod

When I was in the navy I accumulated quite a few of them. One on my gas mask bag, one on my life vest belt, one on my diving bag etc. etc.

A bunkmate thought it would be hilarious to set alarms on all of them to go off every 15 minutes while I was asleep and he was on watch.

I had one of those in the 90's.

It was nearly indestructible. Never left my wrist during daily jogs, showers, swims, saunas ... you name it.

After a few years finally some water had gotten into the housing. The watch was still working, but the screen had become less readable. Still, best watch ever owned.

For me the straps were tearing after about 6-7 years (bought it 2009, might be less plastizer used). Became shower watch for some more years. Sometimes you even forget the stopwatch running for month, but the battery still lasts longer then anything else.
Now I'm wondering if you turn the stopwatch on, if it stores the time it turned on, or if it maintains the 'elapsed seconds'.
That's a smart thought, I haven't had!

Could be testable by turning the stopwatch on and then change the time. I have no idea how these clocks work; if they have a Unix time style counter as internal reference, then this test won't work. Would need a 36 bit memory to run for 20 years continuous counting; 30 billion times bit flipping on the lowest bit. Probably done differently.

I'm wondering why Subcomandante Marcos is wearing two clocks? At first it seems like he put it on his left arm in one picture, and on his right on the other - but on the b/w picture casually "hides" the second clock with his hand.
I used to be a big fan of these watches; cheap, durable, has an alarm and a chronometer, doesn't look completely dorky, and they even acquired a certain coolness factor at some point. When I bought one at a watch store in Turkey, the owner asked me whether I was going to the military; apparently it's pretty much a must have for new conscripts, thanks especially to the alarm that wakes you up for guard duty. I stopped buying new ones, though, because the strap is pretty much guaranteed to rip after a year or so, and a replacement strap costs as much as the watch.
You can replace it with an 18mm nato strap that's never going to break on you!
I used to think these watches would be cool to have, but I just can't justify having a device on my body at all times that only offers a couple features.
> Inventor of the Casio F91W, Ryusuke Moriai, polishes a Samurai sword in Tokyo.

The photo caption is wrong, I think. Ryusuke is not "polishing" a Samurai sword, or Katana. Rather, most likely, he is simply analyzing it and looking at the curvature, etc, and using a cloth to not leave any fingerprint on the blade.