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: https://sweep-hand.org/2012/01/07/this-weeks-featured-watch-19-the-hisonic/), 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!