Seiko 7A38 - by the numbers



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Forum Home > In the beginning there was Seiko Quartz - the World's First .... > Seiko 35SQ (Suwa)

Posts: 59

I recently took receipt of quite a rare Seiko quartz. This is a 35-9010 from February 1971 and is the stainless steel variant of the very first Seiko quartz watch.

I've been trying to solidfy my understanding of the early history of Seiko quartz and the 35 series in particular. The information available on the internet is scant and sometimes contradictory. Below is my current understanding of the 35 series calibres. I'm happy to be challenged and corrected on any of this...


There are two 35 series calibres:

  • 35SQ or 35 or 3500. 3 hands only.
  • 35SQC or 3502. 3 hands plus date (to be expected from the calibre ref).

On the forums, there are multiple references to a 35SQW (implies day + date). This is an error and the calibre does not exist.



There are 4 models.

  • 35-9000. This is what is normally referred to as the "Astron" and corresponds to the original model sold at the end of 1969 for 450000 yen. 18K gold in a cushion case. Some have "Astron" on the dial - at least as late as Jun 1970.
  • 3502-9000. Date version (35SQC) of the above. I don't think that these are ever marked "Astron". In every image of the caseback I have seen, the cases are confusingly marked 35-9000.
  • 35-9010. Stainless steel model, no date. Not marked "Astron".
  • 3502-9010. Stainless steel model with date. Not marked "Astron". 

1800 total production across the four models seems to be right. I am not able to determine the quantity for each model.

Crystal frequency

The early units were certainly 8192 Hz.

An oft repeated claim is that later units were 16384 Hz. For me, this is still in doubt - I have an email from the Seiko museum that claims this is not the case; I have queried this with them and they said that they will "continue to investigate".

Doensen seems to claim that the 3502 is 16384 Hz ( To be honest, I find Doensen's text here to be less than crystal clear. It may have contributed to the general confusion about 8kHz vs 16 kHz and 3500 vs 3502. I have a 3502 from Feb 1971 (ie quite late) and I do not know the frequency. Can anybody suggest how I can ascertain it?



35SQ and 35SQC use a hybrid integrated circuit (so, not monolithic, not CMOS), a stepping motor and ticks 60 times a minute :).

November 19, 2017 at 11:05 AM Flag Quote & Reply

Posts: 13

Hi, selfdater--What a find! It looks to be in great shape, and running. If you get a chance, a movement photo would be appreciated. (I see that the photo of the Daini 35 movement that donwatch was kind enough to post in the 3800 thread is a victim of the photobucket purge; it can be found at, courtesy of JamesA from WUS.)

Thanks for your research into the obscure history of the origins of quartz at Seiko. You've really helped me to grasp the pre-3800 Seiko line-up. At the moment, I'm trying to grasp the post-1970's Seiko developments. They seem pretty obscure to me too--no handy online catalogs, and data is sketchy. For instance, the history of GS on the Grand Seiko site omits the 8J movement entirely.

Anyway, thanks for sharing your great find and expertise. ReggieH 

November 27, 2017 at 7:34 PM Flag Quote & Reply

Posts: 59

Unfortunately, the movement can only be accessed through the crystal. As much as I'd like to see it, I'm not going to get ambitious on this one :)

December 3, 2017 at 5:55 AM Flag Quote & Reply

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