The X8 / Cosmotron electro-mechanical movements first produced in 1966 were, for a short time, Citizen’s most accurate watches – capable of reaching chronometer grade standards. They had a very limited life though, since quartz technology was developed soon after and by the mid-1970s they were obsolete.
The most sophisticated Cosmotron was the 7803A – with a 36,000 beat per hour speed they had an additional feature, indicated by a button at the 8 o’clock position. Known as the ‘special’, this button not only zeros the second hand (to 12 o’clock) but also zeros the minute hand when it is within + or – 3 minutes of 12 o’clock. Currently I’m not aware of any other manufacturer that has employed this feature, which I believe is to allow exact synchronisation of the watch. Also, when the button is held in, the second hand is kept at 12 o’clock until the button is released. If the button is pressed and released the hand is zero’d and immediately restarts, as is found in a ‘fly-back‘ chronograph. Citizen also tells us that the Cosmotron Special is capable of chronometer grade accuracy.
The movement itself is differentiated from other versions by the gold plated finish:
I really like the Cosmotrons – in good condition they are a very accurate timepiece and the hybrid technology they utilise is pretty cool, in my opinion 😉
Sweephand's Vintage Citizen Watch Blog 
Dear Sir. I have in my possession a citizen cosmotron watch which I inherited from my late father. Model no.7803 4-790146 Y 40902176 60-5115 GN-5-5. The watch is in great condition apart from probably needing a new glass face and a new silver oxide battery. I know the watch was working perfectly before the battery expired. Can you kindly give me any indication of costs to fix watch and is there any value within this particular warch. I would appreciate any feedback back as I am oblivious to the vintage watch industry. Regards Campbell.
Hi Campbell, thanks for visiting my blog. The Special Cosmotrons are particularly nice in my opinion, and it’s good to hear you have your father’s watch to wear. Has the battery been replaced and it’s now not working, or do you need to have one fitted? Battery replacement is straightforward if you have a tool to remove the back, though it’s important of course to have the correct battery. I think your watch has a screw down back, so a tool is needed to avoid damage, unlike my example which has a solid case with a battery compartment and a cover that can be unscrewed with a coin. If the watch needs repair/service I can recommend Paul at ‘Electric Watches’ (see the link in my Blogroll on the home page), BUT I know that a few months ago he wasn’t able to take on any new work, so there’s a chance he may still be in that position. The cost of servicing is not too bad, since these are less complicated than mechanical watches, but obviously if parts are needed that adds to the price. I’m not sure what the current cost of a service would be but Paul’s prices are very reasonable. If you haven’t had a new battery fitted, then I can help with that.
Original crystals are (very) hard to find I’m afraid – the part number for yours is 54-60551, but I can’t find anything available at the moment. Even hardened glass crystals like this can be polished if the scratches are light which can improve the look of them significantly.
Cosmotrons are never going to command very high prices, but they do appeal to some collectors/enthusiasts of both electronic and mechanical watches who know about their hybrid design and how good they are. The smooth sweep of the second hand always appeals 🙂 The Special (7803) movement was the last and best of the line in terms of performance and features before quartz rendered them obsolete. I avoid offering views on values here since that could leads to a lot of ‘what’s my watch worth’ questions, and there are many variables which affect value. You can get some idea from searching eBay for Cosmotrons – I would think as well that these are interesting and collectable enough watches to increase in value over the years, if in good condition and running well, so definitely worth looking after.
Stephen
Thank you Stephen for kind reply. I can get the battery ok. The crystal glass has light scratches with two small grazes on the edge. They maybe able to be polished out by reputable jeweller where I live. I come from Ayr Ayrshire in Scotland UK. Will have a go with that avenue first and see what develops. Will keep you posted and thanks for the information you supplied. They are great watches my father liked wearing his. I wear a seiko automatic given to me by my parents in 1976. Lovely watch. Bought in London when on short break I remember. Good luck with your blog. Hope it generates more interest. All the best for 2017. Regards Campbell.
You’re welcome Campbell, and thank you for your good wishes. All the best for 2017, and I hope the Cosmotron will be running well again soon. Stephen
hi Sweephand, nice post, i have the same watch, but the stem doesnt seem to fit inside, im suspecting something is missing , you dont have by chance a picture of the watch with the green cover off? i want to check if my watch missing a part or something is not fitted right
thanks alot
Hi Shadi, thanks for visiting my blog. I don’t have a pic I’m afraid, but maybe these diagrams will help:
Stephen
Stephen, that’s a REALLY cool Cosmo. Thanks for posting it.
And a big thanks for posting all the other Citizens in the past few days. It’s a nice thing to see during the Lockdown Doldrums.
thanks Marvin -it’s fun to choose, fairly randomly, a watch for each day. The only criterion being that it has least got a date complication 🙂 Stephen
Hi Stephen, great blog and details on the Cosmotron, thanks! I understand the 7803A movement uses the lower voltage 1.3V silver oxide cells which are almost impossible to find nowadays. Will the equivalent size 1.5V cells work? What battery would you recommend for this movement?
Sean
Hi Sean, thanks for visiting my blog. 1.5v silver oxide batteries are fine for the 7803, I use Renata 357. Stephen
Thanks Stephen. I left another similar message on another one of your Cosmotron blogs as this message wasn’t showing up after I posted. Feel free to delete. Thanks for your input, I will source a Renata 357. Sean
You’re welcome Sean – I have to approve comments here so there can be a bit of a delay. Stephen