Citizen launched this rather unique vertical-clutch column wheel 8110 chronograph in 1972 - like the 1980 Citizen Ref. 67-9011 Challenge Timer bullhead here, on its original Citizen-signed bracelet - and its compact movement has a high beat, running at 28,800 beats per hour.
 
Significantly, the 8110 movement was Citizen’s answer to Seiko’s famed 6139 movement, with one key difference - Citizen’s well designed 8110, unlike the 6139, featured hand winding and ‘flyback,’ which allows the wearer to zero the chronograph whilst it’s running, rather than having to stop it first, then restart.  This permits an instant stop and re-start of the chronograph function.
 
The compact design of the movement in the 1970's 'flyback' Citizen 8110 "Challenge Timer" automatic bullhead chronograph allowed smaller casing, so the 8110 tends to be lighter than, for example, the Seiko 6139 (which did not have a flyback feature) chronographs of the period.  The 8110 is a far more compact version of the Seiko’s own bullhead design, the 6138-0049.
 
The start and stop of the chronograph is by pressing the button positioned at the 11 o’clock position and is reset by pressing the button at 1 o’clock.  Pressing the reset button without first stopping the chronograph enables instant restart from zero - all models have the column wheel/vertical clutch design.  These movements have quick setting mechanisms for date and day.  Both are set when the crown is pulled out one click -  the date by rotating the crown, the day by pressing the chrono reset button.
 
Compared to modern chronographs, the only chronos in today’s market with similar features and construction sell at a far higher price point – such as Blancpain, Vacheron Constantine, Patek, and Audemars.  The 8110’s are the least expensive, yet most sophisticated chronograph ever made.
 
This Citizen 8110 bullhead comes on its original Citizen bracelet, and with nylon strap, spring bar tool, and rugged travel case.