This Week’s Featured Watch #14 – the Cosmotron 5800

In 1966, Citizen launched Japan’s first electric watch – I featured the Chronomaster version of that in Week 10 – and over the next 10 or so years they developed this electro-mechanical technology via the ‘X8’ and ‘Cosmotron’ lines. With the advent of quartz modules this hybrid technology was short-lived, although it seems to have been successful in terms of sales in Japan.

The design of the electro-mechanical movements changed rapidly as the 1960’s ended and the 1970’s began, with an associated reduction in jeweling and to some extent, prices. As the technology was developed, so the speed of the movements increased. The first ‘Electric’ models (0801 / 0802) ran at 18,000 beats per hour, followed by the 0840 and 4840  running at 21,600 beats per hour. Finally, the 78xx series ran at 36,000 beats per hour.

Well, nearly finally that is, since in 1970 Citizen produced their first electro-mechanical watch for women…..enter the 5800 movement, something of a mini-marvel:

With 17 jewels reflecting a higher grade piece, this movement was used in the ‘IC-12’ ladies model – and solid gold versions of this retailed at JPY180,000! The ‘IC’ part stood for  Integrated Circuit, but the more interesting part is the ’12’, since this indicated the beat of the watch, a remarkable 12 beats per second…..or 43,200 beats per hour.

The 5800 movement was / is Citizen’s highest speed watch with a mechanical balance, and was used later, around 1974/5 in a version for men. Here’s the gold plated version, from August 1975:

The small movement is held by a plastic internal case:

This is the stainless steel version:

Produced in November 1974, this one has a different style of case back, one that actually looks later than the 1975 model:

The plain white dials and black frame hands combine well:

And just in is a women’s model from 1970 – sadly not the IC-12 Chronometer version! Only one quick shot so far, to show the size against the men’s model:

The 5800 movement is not so well-known in the Cosmotron line-up, but is an excellent example of the hybrid technology pursued by Citizen just prior to the quartz explosion.

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24 Responses to This Week’s Featured Watch #14 – the Cosmotron 5800

  1. dennis says:

    recently acquired the men tank version with the 5835 movement inside – well that’s the number engraved on the caseback so I think that’s the movement inside. Could you be able to find more info based on the other numbers on the caseback?

    4-350243 YO


    • sweephand says:

      Hi Dennis, thanks for visiting my blog. As far as I know, the 5835 movement was later version of the 5800 electro-mechanical calibres, with hour and minute hands only, and no second hand. The 5800 is one of the hybrid movements, as used in the X8/Cosmotron line of watches, featuring battery powered circuitry and a hairspring with magnets rather than conventional mechanics. The 5800 was introduced in the ‘IC12’ watch, i.e. Integrated Circuit / 12 beats per Second, making it the highest beat watch before quartz technology revolutionised things. See here for more info:

      So the markings on the case back include ‘electronic’ as per the Cosmotrons as well as the standard marks. The case number – 4-350243 – gives a clue to the movement inside, but it’s not that obvious unless you know that ‘4-35’ was used for the 5835 models. These were made in the 1970s, but only for a short while since they were overtaken by quartz, so the first three numbers in the serial number tell us that it was made in December 1974.


  2. dennis says:

    Cheers mate! That was much appreciated. 🙂

  3. dennis says:

    Quite OT but did Citizen ever released the 24 hours watch?
    Recently I was given Seiko Levante 24 hour watch and it is very unique and peculiar watch.
    And this got me thinking whether Citizen ever released something similar but my search came up with nothing.


  4. dennis says:

    with scorching 37/38 degree Celcius over here got me thinking it’d be good idea to get the metal bracelet rather than the leather band. Did Citizen have the stainless steel bracelet common in its range or was the each watch had its own unique bracelet? Mine’s 18mm lug width and give its square shape think I will need straight end SS signed bracelet.

    However was this type of watch ever came with the metal bracelet? If it never came with in the first place I might need some suitable alternative – not costing arms and legs. 🙂

  5. Hunter Schultz says:

    Hello Stephen,

    Any idea of where to have these movements serviced? It seems they should be rather simple to service, but looks are only a part of the story — one that deserves your magic touch…

    Are there any service manuals?

    My wife is now the owner of a 4-580222. In the mail now.

    I am very curious to see how the second hand moves. Very smooth or standard five BPS?



    • sweephand says:

      Hi Hunter – thanks for visiting my blog. Interesting to see that you have a 5800 on the way. Don’t hear much about these rather neat little movements, and they were the smallest ‘electronic’ movements in the world at the time. They run at 12 beats per second, so the sweep is smoother than the average mechanical. They are not completely smooth, but still very nice 🙂

      The only person servicing the Cosmotrons that I know is Paul at Electric Watches, in the UK – see the link in the blogroll in the right hand panel of the home page. BUT he has had a nasty hand injury and is only now recovering and getting back to watch servicing, so he may not be able to take any new work for a while. On his contact page he says he may be back in action around now so worth contacting to check. I can highly recommend him. I’m not sure whether he has got his hands on a 5800 before though, so that’s also something to ask him about.

      I have a technical manual for the X8 Cosmotron, covering the 4840, 0840 and 0880 movements, but not the 5800. I am not a watchmaker so I may be wrong, but I would think the mechanical parts and servicing requirements are similar. I haven’t seen the manual again on the internet since I got it some years ago on eBay. Happy to get it scanned for you if you are interested.


  6. Hi Stephen, Well, add another men’s model to your list 🙂 5800-580390K. Just arrived along with the smaller one for my wife. The man’s version is a classic 1970s cushion case watch. Can send photos. At least the before shots. Cleaning commences shortly then I will take them to Citizen to open them up and see if new batteries will work. Crystals need polishing as replacement for now is essentially not an option. Cheers, Hunter

  7. Raveen says:

    Hi Stephen, does all Cosmotron series have the same battery models?
    Does the 5800 use the same battery as Tuning fork models?

  8. siamdao says:

    Just received two watches, both men’s. A 1975 Citizen Electronic Cosmotron 5800 white dial with second hand and a 1976 Citizen Electronic 5835 blue dial no second hand. 🙂 🙂

  9. Raymond V says:

    Hi. I’ve been playing around with the I-12 movement for a while. I need the part numbers for the coils. Can you help?

    Thank you.

    • sweephand says:

      Hi Raymond, I’m afraid I don’t have the part numbers. I don’t know where you’d find them either, so sorry I can’t be of any help at all! Stephen

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