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This is one of the two vintage automatic chronograph movements made by Citizen, the other is the Citizen 8110A calibre that features an extra 12 hours counter.
A video of 8110A is here:
And here is the video for 67-9631, calibre 8100A. You can see the start-stop-reset mechanism in function, as well as the fly back. Also you can see the way you can change the date and the day. Enjoy!
More informations about this watch here:
Citizen had two automatic calibres.
One automatic chronograph is the 8110A and you can read about the “octagon bullhead” that had this movement here:
And the other one is the one I will write about now, the 8100A.
Both of them came with different case design, shapes and sizes with a lot of dials. This is why sometimes is difficult to identify if a certain watch is correct or “reconditioned” with aftermarket parts.
This is a one sub-dial design chronograph featuring a lot of interesting details. It was made in November 1973.
The case is made of brushed and polished stainless steel. The chronograph pushers are on the side, where the winding crown is. It is a cushion shape with a circular grain brushed front surface (I have seen a sunburst grain also, and polished – the polished is for sure not correct) and polished everywhere else. The caseback is screw in with a circular brushed flat surface. The crown is signed “CTZ”. The mineral crystal sits a little bit taller than the case, with chamfer edge. Nothing out of the ordinary, jut a simple, normal ’70’s design by Citizen, 38mm wide without the crown.
The dial is blue with orange and silver accents. It is nothing less but gorgeous! The blue changes from dark blue (almost black sometimes) to bright blue and then to a type of green really difficult to picture. Sometimes it seems unreal. You have to see one in real life in order to fully appreciate the beauty of this one. On 6 it is the sub-dial, counting the elapsed (30) minutes. This is the only sub-dial (normal for cal 8100A). The central, orange central sweeping hand counts the seconds. This sub-dial is silver with highlighted 5 minutes periods. The 5-10 minutes is blue. Not only the chronograph hands are orange but also the current time hands are painted (not entirely) orange and they have a luminous line. On 3 o’clock there are the day and the date windows, with a silver painted frame. The days and the dates are printed on black disks. The polished Citizen logo is applied and so are the hour markers. The hour markers have an orange central line ending with a luminous dot. On the outer side of the dial there is a white Tachymeter scale, for racing, you know!
The movement is the Citizen automatic, 23 jewls, calibre 8100A with hand winding capability. It was produced by Citizen starting from 1972, just as 8110A. It is a vertical clutch chronograph (beating at 28.800 bph) with column wheel and fly back function. It also features a day and date indicator. The fly back function means that you can reset the chronograph while in motion and it will start again without needing to go the entire process of pressing stop-reset-start. So, one push can do all of this. Of course that if you want to stop it you can go the classic stop-reset way. A particularity for this movement is that when you want to change the day you should pull the crown to second position (for changing the date) and push and release the reset (5 o’clock) button. It is 27 mm wide and 5,8mm high, (1mm less than 8110A). The column wheel/vertical clutch design of the movement advices to leave the chronograph running for most of the time (this way you can also see the beautiful sweeping central second hand in movement), but from time to time it should be stopped. This is a chronograph that needs to be used. It is not made for design purpose but for timing.
The bracelet is an usual one piece link design, made by Citizen, with a brushed surface that suits the watch perfectly. It is made in stainless steel with a signed “Citizen” clasp. As usual, Citizen bracelets are very comfortable with a lot of adjustments so finding the perfect fit is easy.
Conclusion: Wonderful Citizen chronograph, vintage yet so modern, with a nice wrist presence and amazing dial!
Enjoy the video of this watch here: