Seiko's Cal. 38 series were the first volume-production quartz movements from Seiko, and set the template for all future quartz movements. This series was produced from 1971 through the late 1970s, with many enhancements over the years.
Seiko was quietly racing to develop a quartz watch movement in the 1960s, and delivered their first Cal. 35 movement to the Neuchatel Observatory in late 1967, just a few months after the CEH delivered their "Beta" quartz movement prototypes. A product of Suwa Seikosha Cal. 35 used a 8,192 Hz of 16,384 Hz quartz crystal and an integrated circuit from Intersil in the USA. Seiko offered Cal. 35 SQ for sale in the Seiko Astron watch on Christmas Day, 1969, with 100 examples sold in the first month. Suwa rival Daini Seikosha developed Cal. 36 and launched it in 1970, but neither movement was truly produced in volume.
Suwa Seikosha developed Cal. 38 as a full-production midrange to high-end quartz movement, and it incorporates many features that now seem commonplace but were groundbreaking at the time. The quartz crystal oscillated at 16,384 Hz and it used a CMOS integrated circuit to reduce battery consumption, though later examples used a 32 KHz crystal. The hands were operated by a stepper motor and a jeweled backlash pin ensured a smooth dead beat seconds hand. The earliest examples were sold as "VFA" ("Very Fine Adjustment") and were adjusted for temperature and in 6 positions.
Early examples of Cal. 3823 use a large 16 KHz quartz tube and unusual "step variable condenser" regulation system using multiple contacts for variable resistance. The design was evolved over time to use a more integrated quartz module and smaller ICs as technology advanced. The final Cal. 3823A had a small 32 KHz quartz tube and modern screw-type trimmer condenser for adjustment. The circuit block and crystal oscillator were also combined in later examples. These components could be retrofitted to earlier movements, and many were during service. 16 KHz examples are rare today.
Cal. 380x were the lower-end movements but were still accurate to 2 minutes per year. However these movements lacked any adjustment beyond replacement of the condenser block. Cal. 382x included a thermocompensation circuit and was accurate to 1 minute per year. It could be regulated using a step variable condenser. All basic movements used 7 jewels: Two each on the third wheel, sweep second wheel, and step rotor, and another used on the seconds hand finger.
All 38x3 movements were branded "38SQW" or "38QTW" and included day and date. Cal. 38x2 is branded "38QTC" and is date-only. Cal. 38x0 was branded "38SQ" and lacks the calendar function.
These movements were produced in larger volume but were still quite high-end compared to mass-market quartz watches later in the 1970s.
The 38SQ "VFA" line was replaced by the 48GQ "Grand Quartz" and 48SQ "Superior" line. The 38QT "QT" line was replaced by the 08KQ "King Quartz", 38QR "Lord Quartz", and 08QT line. The QR line of watches were replaced by the cheaper "Type II" models.
- 3800/3802/3803 (1971) - "Seiko QT" line - Regulation by replacement of condensers; accuracy to less than 2 minutes per year
- 3800 - 38QT - time-only
- 3802 - 38QTC - date
- 3803 - 38QTW - day/date
- 3819 - 38DQC - "Duo Time" - Central GMT hand and date (part of the "QT" line)
- 3820/3823A (1971) - "Seiko VFA" line - Step variable condenser; temperature compensation; accuracy to less than 1 minute per year
- 3820 - 38SQ - time-only
- 3823 - 38SQW - day/date
- 3862/3863 - "Seiko QR" line - Oscillation regulation condenser or trimmer condenser
- 3862 - 38QRC - date
- 3863 - 38QRW - day/date
- 3882/3883 G.F.A. - "Seiko Superior"