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quartz seventies of the calibers twin

The twin quartz calibers of the seventies
When quartz was well established, at the end of the Seventies, the Seiko 1978 JDM catalogue showed the twin quartz caliber for the first time, however there were (eventually) at least three different design technologies behind the Seiko twin quartz models.
While quartz based watches are extremely accurate compared to mechanical watches they are still not perfect. One of the main reasons for the inaccuracy in a quartz model is because as the temperature changes the oscillation of the quartz crystal varies slightly. This change in oscillation will cause the slight drift in timing. To compensate for these changes quartz watches will employ some kind of temperature compensation.
The five calibers
In all five different calibre series were introduced in less than two and a half years, they were used in the Superior, Grand, King and Quartz line ups. The 99 series was first released in August 1978 (specifically the 9983A), the 92 series released in December 1978, closely followed by the 97 series released in October 1979 (9722A, 9723A). Just under a year later the 96 series was released in September 1980 as caliber 9641A and 9642, the latter in the inconspicuous Seiko Quartz - a true wolf in sheep’s clothes. Hot on its heels was the 94 series released in November of 1980 (9441A).
The product lines


Let’s start with the Superior line (above), caliber 9983. This was a movement with an accuracy rating of 5 seconds per year, among the best Seiko has ever produced. At that time, the Grand Quartz line from Suwa benefits from this twin quartz innovation with the twin 9943 and the 9940 caliber - retiring the caliber 4843 that had just been selling for two years (1976-1978). The most expensive models however, are still in the Superior line, with a price tag of 235,000 Yen. The King Quartz line however with the 992x, 972x, 922x and 96 caliber, is no slouch here compared to its high rolling brethren.
Grand Quartz
In 1978 the aforementioned caliber, the 9940, was first produced, right next to a more expensive mysterious caliber from Daini, the 9256 (last seen 1981). That watch could cost you about 1380 dollars nowadays for the superbly dialed 9256-5010 model. Grand Seiko money indeed.
With an accuracy rated at 10spy - the same as today's Grand Seiko cal. 9F - the 9940 (and the 9256) is shown for the first time in the JDM 1979 V2 catalogue, on page 6 priced at 75,000 Yen. In todays money that would be some 940 dollars. There's only one other reference with the cal. 9940 in the catalogue and it is on page 4, the 9940-8010 with gold-plated case, leather and gold dial, setting you back 90,000 yen. There are minimal changes in the next few years until finally 1985, after which both the Superior and Grand Quartz lines aren't present anymore in the catalogue - moreover, there are no other models with twin quartz calibers on it. In 1986, one might say, Seiko went crazy, introducing scores of goofy product lines like “Isnt” and “Off”, listing it right after each other in the catalogue; "Seiko isn’t off"… seriously?
Back to caliber 9940. It is probable that the entire production of the Grand Quartz line spans a decade, 1975-1985. For caliber 9940/9943 however just 6 years. All of these watches have the strong lines and angles tipical of the Seiko productions of the Seventies. The dial has the indices and the Seiko logo both applied and at six o'clock there is the "double honeycomb" logo, indicating the presence of a "twin quartz" caliber inside.     


A feature of this particular caliber - you guessed it - is the total absence of any day and date indication; maybe this is why watches running the 9940 are quite scarce, watches made with the 9943 (day/date) are more common. Remember, during the entire production run we have only two 9940 models, but thirteen with the 9943 and two with the date-only 9942.
Another feature is the way that the 99 series twin quartz models work. These models use one of the crystals for the timing accuracy and the second crystal is used to detect the temperature. These two values are then combined in a processor to calculate the correct timing offset. This method allowed extremely accurate adjustments with all the models achieving the following yearly variations, 9980A and 9983A +-5 seconds (Superior), 9940A 9942A and 9943A +-10 seconds (Grand Quartz) and the 9920A 9921A and 9923A +-20 seconds (inc. King Quartz).
King Quartz (KQ)

The 97 series implements twin quartz by using two paired crystals with different thermal characteristics. The temperature variation between the crystals are then averaged to provide accurate measurements over a wide temperature range. By using this method the yearly variation for the 97 series (9721A, 9722A, 9723A) King Quartz models are rated at +-20 seconds per year.

Let’s not forget the 92 series (9223, 9256A) and the 96, there are no specifics on it but as the 92 were rated at +-10 seconds per year I am guessing these were similar to the 99 series design.

The 96 series were rated at +-20 seconds per year so may have a similar design as the 97 series.

The 94 series King Quartz models were first released in November 1980 (9441A, 9443). These models have the two crystals running at different frequencies, 32kHz and 40kHz. The first model (9441A) was rated at +-20 seconds per year but by April 1981 (surprise) the 9481A was released and rated at +-5 seconds per year and fitted to Superior models. Last but not least, there was the caliber 9442, assigned to the Lassales (described seperateley).

The 9923 was a bit of an odd caliber for the King Quartz, as the base caliber 99 was represented in the Grand Quartz 9940 and in the Superior line 9980/83. Shown to the left is the very refined looking model 8050, of which some color variations were made, like the mahogany striped dial. (Below).

On a more general note, Seiko more often than not delivered a surprise caliber that was used in multiple watches. It is hard to tell in which way the base caliber was changed apart from accuracy indications.
The brown or black croc-leather band supplied should have a vintage and Seiko-signed (gold plated) buckle. On catalogues pictures of Grand Quartz, watches have either a GQ-signed buckle or a Seiko-signed one. Sometimes one can see the double honeycomb symbol.
Seiko King Quartzes with one or the two oscillators are interesting watches, the latter I think only from the Daini division. Very accurate too as you might expect of two time sources (crystals) and thermo compensation.

These quartzes could sport very funky dials, including a very nice blue jeans from 1978. 


In this small and rather inexpensive group of high end quartz models the oldest  thermo compensation method (probably before 1978) is the one present in caliber 5856. The method is based on having two quartz crystals, both at around 32 kHz. The difference between them is used as a way to indirectly measure temperature - and from that the number of quartz ticks that need to be skipped in order to achieve better accuracy.
Adminishing the #$@ out of it
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  • Omegaist
Very nice review indeed...

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