Well, it’s not one watch today in fact, but a group shot to celebrate Citizen’s line of hybrid watches first launched in 1966. The X8, just called the Electric Watch at the very beginning, was Citizen’s first battery powered watch, but retained a relatively conventional hairspring oscillated by magnets. The Cosmotron name was introduced in 1969, as Citizen developed the technology and raised the beats per hour to 36,000 in the 78 series and 43,200 in the 58 movement. The magnet driven hairspring was even retained for Citizen’s first quartz watch in 1972 which geared the quartz oscillation down to 57,600 beats per hour – a design produced only for a couple of years at most when it was replaced by fully electronic modules. The X8 Cosmotron line was produced only for about 10 years, its days were numbered as soon as quartz technology was applied to wristwatches, which for me makes it all the more interesting. There is an odd one out in the Cosmotron line-up though, and that is the GX. The movement in this is unlike any of the others since it is an in-house single coil tuning fork design. Citizen’s commercial arrangement with Bulova allowed them to make tuning fork movements under licence, and indeed they made and supplied parts for Bulova. But the GX’s 3701B movement was designed as well as built by Citizen – visually the difference from Bulova’s single coil version, the 319, is that the coil is placed on the opposite side. I don’t know why Citizen chose to call this ‘hummer’ a Cosmotron, rather than Hisonic – maybe it was linked to the contract terms with Bulova.
This group has examples from the evolution of the X8 Cosmotron, from the X8 Chronomaster (08 calibre) to the Cosmotron Special (78 calibre), the 58 calibre high beats and the GX (3701 calibre). Notable pieces here are the Chronomaster in the box, the rare chronometer model just left of centre with the light tan strap, and the GX just right of centre on its original beads of rice bracelet. And in the centre, with its blue dial, is the world’s first watch to be housed in a titanium case. This is an X8 Officially Certified Chronometer and is one of the less than 2000 pieces that were made in 1970:
More info on the X8 Cosmotrons here: https://sweep-hand.org/the-x8-cosmotron/