Time for a more complicated watch to be featured, and this one is one of the 8110A mechanical chronographs from the 1970s. The Challenge Timers, aka the ‘bullhead’ are the models most often seen for sale, many with after market dials and re-finished cases (see the buying guide: https://sweep-hand.org/want-an-original-citizen-bullhead-a-quick-buying-guide/). There are a number of other models though which are not so often seen, and the all stainless steel 67-9151 is one of those:
This model has an interesting case shape as well as hexagonal sub-registers, a dial design shared with one other model, the 67-9178 (see all of the models on the chronograph page: https://sweep-hand.org/citizens-vintage-chronographs/)
The shaded green dial and contrasting yellow and orange sub-register borders, combined with the other design features are very 1970s. I have seen some very faded dials on these, and some which appear to have only yellow borders and more even colouring on the dial. Although they have the same dial code I am not sure whether they were a different original design, or have suffered a degree of fading – although two case numbers are seen on these so there may have been two versions (4-901118 and 4-901142).
My example was made in January 1975, and looks to be on an original solid link bracelet:
The clasp is signed:
Detail of the sides and signed crown:
The 8110A has a high beat movement, with hour and minute sub-registers, and ‘flyback’ capability in a compact design, features that represent a very good quality watch.