Casio CFX-400

Casio CFX-400

Casio produced their first scientific calculator watch in 1983, the CFX-20 (resin case) and CFX-200 (metal case) which, while getting rarer and more expensive, can still be found in varying condition on eBay without looking too hard.

Then, in 1984 or 1985, they started producing watches with a membrane keypad, including databanks like the DBC-60/600, the thin CFS-80, accountant’s friend CBA-10 and, unfortunately, the updated scientific calculator watches CFX-40 (resin case) and CFX-400 (metal case).

The calculator watches with buttons that sat proud of the keypad, that had served them so well for five years across a range of different models including the original CFX watches, were far better than this replacement keypad that faded and cracked with use.

As a result, the CFX-40/400 is a real rarity in any condition, particularly if you’re seeking one with a usable keypad.

Some enthusiastic designers have come up with a partial workaround, producing replacement vinyl adhesive keypads to stick over the old ones but they don’t quite match the originals and are, themselves, quite fragile. Much like the after-market G-Shock bezels being produced in China and Brazil, they look good from a distance but not on closer inspection. However, they are definitely better than nothing.

The watch pictured here started life as a CFX-40 but the keypad had cracked and the numbers all but disappeared. The seller said it was worse before he had given the keypad a cursory spit and polish and, while it was able to be coaxed back into life, it’s pretty much unusable other than a basic 8-digit calculator if you can’t see the other symbols on the keys.

NOS cases appear on eBay very rarely and are quickly snapped up so I wasn’t particularly confident when putting out some feelers to see if I could find a replacement — I was quite sure the best I’d be able to find was one of the after-market vinyl keypad overlays.

But, occasionally miracles happen, and a Spanish seller had a NOS case for a CFX-400 with the white/yellow keypad. More incredible still he had a NOS black keypad as well which he bundled with it. Overall it was an expensive transaction, but the chances of finding another are not great so worth every cent.

Those familiar with the CFX-400 will be well-aware of the range of available functions it holds, and for mathematicians, engineers, and people who just like doing calculations in baseⁿ it’s in a class of its own. Other than the CFX-20/200 and a scientific calculator watch Citizen made, there’s nothing else like it. It’s features seem to parallel the widely-popular desktop calculator Casio FX-82, but having it on our wrist adds another dimension.

Obviously with the invention of smart watches, having a wristwatch calculator is not only possible, but has far more functionality than this. But the CFX-400 was made more than 30 years ago.

An excellent watch, well-deserving of the high prices good examples command on eBay.

Here’s the CFX-40 and 400 from the 1985 Casio catalogue, along with 1983’s CFX-200, the thin CFS-80 and two of the many QW437 variations, the CA-50 and CA-502.

Interestingly, the catalog has the CFX-400 with a very white keypad — I’ve never seen a real one with a keypad this white and even NOS ‘white’ keypads tend to have a yellow tint. The stark white looks very nice though and blends well with the silver case.

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20 Responses to Casio CFX-400

  1. I found a Casio CFX-200 that I bought back in the 1980s. I just had a jeweler put a new battery in it and clean it up. It’s in great shape. What range of values do you think it’s worth? Thanks. Sam

    • Hi Sam, that’s a good score! The CFX-200 is hot at the moment so, depending on condition, you could get anywhere from USD50 to USD400. Condition is everything though so make it shine with a microfibre cloth and take good photos when you list it.

    • If you list it on eBay for $1 reserve, you’ll find out exactly what it’s worth 🙂

      It’s pretty much worth whatever someone will pay you for it. I’ve seen them go for close to USD2000 and as little as USD100 so it really depends who finds your auction and who they’re bidding against.

      Good luck!!

  2. I see a CFX 200 unused not a scratch on it still in its original box on E-Bay asking $900 or best offer.

    What would you consider a reasonable offer to be?

    • Personally, I wouldn’t offer anything near $900 even for a NOS example.

      Mostly because they aren’t that rare; if you search eBay for cfx200 there are plenty of them on there at the moment, in varying conditions, for a range of prices.

      There’s one listed as ‘nearly immaculate’ that looks pretty good with an opening bid of $225 and checking completed listings shows that mint examples can be bought for well under $300.

      If you really want the original box and papers you’ll pay more for them, but not $600 more!

      It’s different strokes for different folks though. If money isn’t a problem and you are desperate to buy a near-new example, then you’d probably stump up $900. That’s just not what I’d do 🙂

  3. I have 2 cfx-400 (1 in package) both working and i have too a cfx20 working, What range of values do you think it’s worth?

    • There hasn’t been a NOS CFX-400 for sale for a while, you could realise good money for that — particularly if you get two bidders battling for it. The CFX-200 is relatively common but still sells for a good price.

      Depending on condition, USD80-300 for the CFX-200 and USD150-350 for the unboxed CFX-400 and USD200-??? for the boxed one.

  4. I have a cfx-40 that the crystal just broke the other day. Need to take it somewhere but not sure where

    • Hi, contact an eBay seller called dimar2018 — he sells a lot of NOS parts for vintage Casios and is where I was able to get a case for my CFX-400 from. If he doesn’t have one, your best bet is to set up an eBay search and have a lot of patience! I have a spare CFX-40 case somewhere but from memory it has a small crack in the crystal too.

  5. I purchased a CFX-20 at an estate sale for $5. All buttons intact, but can’t figure out how to take the back off to check if a new battery will bring it back to life. Got a steal regardless, just doing some hardcore research to see what this piece of history is worth.

    • Good score — even for parts. To open, look at the four corners of the caseback. One of them will have a small notch under it, just big enough to get a case knife (or small screwdriver) in it. Insert, twist, and it will pop open. Take your time and use the right tool to avoid damaging it. Also get yourself a CR2016 battery in the meantime (it originally took a BR2020 battery but these are very hard to find now and the 2016 does the job fine).

  6. I immediately purchased a CFX-400 for $ 69 that had not been confirmed to work.
    Fortunately, there was a problem with the appearance and the decal switch.
    The body is made of DBC-600 ($ 0.99) decals made and attached.

    The only difference between the CFX-400 and the DBC-600 is the number of modules, glasses, and watchbands.

    The repair process was posted on my blog

    I am a South Korean so I posted in my native language

  7. I have a CFX-400 close to perfect condition. Interested to know what would be the market selling price for this historic jewel… any ideas??

    Which would be the best place? Ebay? is there anything more ‘specialized’?

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