This Week’s Featured Watch #33 – The Cosmotron GX

In 1969 Citizen’s electro-mechanical watches, introduced in 1966, became known as ‘Cosmotrons’. The technology in these combined new printed circuitry and a battery with a relatively conventional balance and hairspring. But one Cosmotron was an exception to this convention – the ‘GX’ – since this was in fact a very different animal, in that it was a tuning fork watch.

Citizen’s tuning fork watches were known as ‘Hisonics’ (see my example here:, so I’m not sure why Citizen chose to place the GX in the Cosmotron line.

Originally developed in the USA by Bulova, the tuning fork technology was an innovation that turned the 360 vibrations per second of a tiny tuning fork into circular movement, resulting in much greater and guaranteed accuracy that even the best mechanical watches couldn’t match. The equivalent Bulova movement to the Hisonic is the 218, whilst the equivalent for the GX is the 219. However quartz technology soon eclipsed even the tuning fork’s time-keeping qualities, so the Hisonic and Cosmotron GX models enjoyed only short production runs in the mid-1970s.

The GX is now a fairly rare piece, and is seen less often for sale than the Hisonic. My example is from November 1975:

The dial carries the unique GX applied logo:

The case back is plainer than the Hisonic models, some of which carried a gold medallion, and is a simple snap on design. This one is engraved, possibly to celebrate 15 years of service – I believe with the Yashica camera company. The serial number confirms November 1975 production:

The 3701B movement has 11 jewels rather than the 15 found in the Hisonic, and the movement is not stamped ‘LIC. BULOVA’ . The crown is signed (CTZ) and in normal position the date can be quickset, at one click out the watch is hacked and time can be set, at second click (fully out) the battery is fully disconnected when the watch is not in use:

However one of the most obvious differences is that only one coil is used:

And cheaper plastic is in evidence rather than the copper plate seen in the Hisonic:

The lower jeweling, use of a single coil, greater use of plastic and plain case back are clear evidence that cost savings were applied to this model, and maybe this is why Citizen branded it a Cosmotron, keeping the Hisonic as a more exclusive high end piece.

Whatever the reasons, the movement functions perfectly well!

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4 Responses to This Week’s Featured Watch #33 – The Cosmotron GX

  1. Rob says:

    Hi Stephen.
    Could you de-code this for me please? Does the Japan mean it’s a JDM model?
    Citizen Cosomotron GX. Below is, as it’s laid out, on a plain back. (press on)
    4-370660 Y

    Thanks very much. Regards, Rob….

    • sweephand says:

      Hi Rob, thanks for visiting my blog, and apologies for my slow reply. Congrats on acquiring a GX – these are nice watches, and not very common. Other than the obvious info on the back, here is what the other stuff means:
      4-370660 Y – the case number, with ’37’ indicating the movement inside, which is a 3701B. I’m not sure about ‘Y’, maybe a factory code
      51200494 – the serial number, provding a production date of Devember 1975 (‘512’)
      GN-3-U – the case type, meaning a water resistant model
      JAPAN – made in Japan, rather than being for the JDM.


  2. Rob says:

    Hi Stephen, thanks for that.
    I must admit, I quite like the GXs, that’s four I have now. The reason I mentioned the “Japan” is that I’ve seen some cases without Japan on. The only thing I don’t like about the GXs I have, is that all the case backs have been a real so and so to get off and causing much swearing.

    • sweephand says:

      Hi Rob – the case backs are indeed a pain to remove. I thought these had one piece cases for a long time before having another look and managing to get one off! I’ve had a look at my watches and it looks like the GX’s are the only ones I have with JAPAN on the back. I have seen one non-GX Cosmotron with JAPAN on the back. So, not sure why these are different – on reflection maybe they were JDM only….

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