Citizen Cosmotron Special 7803 Calibre

In the 60s and 70s, Citizen produced two main lines of electronic watch. One was the tuning fork controlled HiSonic range (which I've blogged an example of previously), and the other was the Cosmotron range which today's watch is from.

The Cosmotron watches were a transistor controlled balance wheel movement design with started in 1966 (and was Japan's first electronic watch). This type of electronic watch became obsolete in the early 70s due to the start of the quartz revolution. The front dial has the text Citizen Electronic, and Cosmotron along with a lightning bolt symbol used for the Citizen Electronic watches.

The range is a 3 hand dial design, with a high beat seconds hand. This one is part of the 7800 movement range which were first released in 1972 (which is when I think my one is from). These models had a day and date at the 3 o'clock position, and worked at 36,000 beats per hour (double the speed of the first, Cosmotron). Setting the day or date is done by pressing in the crown, and which one changes depends on which way up you hold the watch (12 pointing up sets the date while holding upside down (6 pointing up) sets the day). I guess this is to allow easy synchronisation of the watch (to ensure correct time or to make sure multiple watches read the same).

After a bit of research, it seems this is actually a Cosmotron Special with a 7803 movement. This model can be identified by an additional button at the 8 o'clock position. When the button is pressed, it resets the seconds hand to zero (12 o'clock), and a long press holds the hand there until it is released. If the minutes hand is within +/-3 minutes of the hour, this is also set to 0.

This version also has a monocoque (one piece) case, so you need to remove the crystal to get to the movement. The battery is replaced through a coin opening battery compartment on the back, and there is also a screw opening cover to get to the balance adjustment screw.

The full model number is 7800-870115.