Citizen Costmotron Hybrid Watch 1970s 7804

This is a Citizen Cosmotron watch from the 1970s.

The Cosmotron is a mostly mechanical movement but powered by a battery. These were out at the same time as the very first quartz watches.  The movement in this one is a 7804. It is a mechanical movement with a balance wheel but instead of a mainspring and barrel, it has a battery. The battery goes though a circuit with a transistor to a coil. The coil is sandwiched between two wheels on the balance wheel assembly, one wheel has magnets on them  (yes magnets in a mechanical watch!) the coil pulses with the current and the magnets are opposite poles which makes the balance swing. The movement of the balance then transfers its power down the train of wheels, eventually to the hands, in effect moving the opposite way to any conventional mechanical watch which goes from mainspring to balance wheel.  This regulated pulse makes the watch run efficiently and more accurately.  Also gives a sweep second.  The joy of these is you can take them off for weeks at a time and they will just keep going, ever ready to wear! 
This model has its original crystal still fitted.  I have completely cleaned and serviced the movement. New gasket has also been fitted.  I have lightly polished the case and re-brushed the lugs but not to remove any of the scratches and patina.  I have finished the look with a new blue leather strap with steel buckle.

The watch party piece is its quick-set of day and date.  Done by gravity. Hold the watch in your hand and push in the crown and the date will change.  turn the watch upside down so 6 it at the top and push the crown in again and the day wheel will change!  it has both Kanji and English as options. 
As a vintage watch I would class it as not waterproof so refrain from swimming or bathing wearing this on

Please watch all of the videos in this listing to see an in-hand review along with movement running and timegrapher trace.  Please note that in an electronic balance movement amplitude and beat are not so important as the amplitude is governed by the pulse from the coil. 

Dimensions

Diameter 37mm

Thickness 13mm

Lug Width - 18mm  

USA buyers will be subject to tariff which is 15% of the value of the watch and has to be collected at point of sale.