In 1970 Citizen produced two chronometer grade models in their electro-mechanical X8 Cosmotron range. One of these is the very rare titanium cased version, of which only 2000 were produced – it was the first watch globally to be made from titanium – I haven’t got one of those! See here for some images: https://sweep-hand.org/2011/05/25/japanese-auctions/
The other model is a little less scarce, and I managed to get hold of one of these some time ago:
The official certification was to the Japan Chronometer Association standard (rather than the Swiss COSC) but this is likely to have been no lower than the Swiss standard and may have been higher. The dial is marked accordingly:
The case is unique to this model, and is certainly unusual:
The case back is generally typical, showing production in August 1970, but it lacks ‘parawater’:
The 0820 movement was first produced in 1970, and has 19 jewels – it runs at 21,600 beats per hour, faster than the first of the electronic movements but slower than its successor which was upped to 36,000 bph. As with all chronometer grade models the movement is uniquely numbered (the 1.55v battery is missing in this pic):
This model retailed at JPY36,000 in 1970, more than the X8 Chrono Master, reflecting the grade this watch achieved. It was, however a short-lived piece, soon replaced by the next Cosmotron movement (the 7800 series) – whilst the whole of this hybrid technology was rendered obsolete when the quartz revolution began in the mid-1970s.
More info on the Cosmotrons can be found on this page: https://sweep-hand.org/the-x8-cosmotron/