Seiko's Cal. 39 series were early high-end quartz movements from Daini Seikosha. Just two movements were released in this family, which includes a flashing LED that serves as a running indicator and used an electromagnetic escapement rather than a stepper motor.

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 advanced features including a CMOS integrated circuit and 16 KHz or 32 KHz crystal.

Daini's second quartz movement was Cal. 39, a high-end movement that competed with the best from the Cal. 38 family. Cal. 39 movements feature a flashing LED to serve as a running indicator prominently featured on the dial above the 1 00 marker. The 39SQ line was differentiated mainly by the rectangular cases, which were quite different from the “shield” style round watches in the 38SQ line. This is due to the rectangular shape of the movement, which includes two batteries.

The design of the movement is extremely unusual, using an electro-mechanical escapement rather than a stepper motor. Two large coils alternately pull a jeweled finger once per second, with a simple lever also used to prevent backlash of the seconds hand. This design is reminiscent of some of the earlier CEH Beta series movements as well as the Bulova Accutron and other contemporary electro-mechanical movements designs. It is entirely unlike any later quartz movement.

Cal. 3922 was released first, adjusted to VFA accuracy of +/- 10 seconds per month. Introduced in November 1972, this movement was sold alongside the similar Cal. 3823 in the “SQ” range of watches. Cal. 3922 featured a date wheel.

Cal. 3923 appeared in 1973 using the 39SQW name. This movement featured a day wheel in addition to the date wheel found on Cal. 3922. Both movements are featured in Seiko's 1973 catalogs, suggesting an earlier date than that listed in other sources.

These movements were produced through 1976, after which they are removed from the Seiko catalog. By this time, they were superseded by more advanced movements that were thinner, more efficient, and cheaper. And no watch again would include the flashing LED.

• 3922/3923 (1971-1976) - “Seiko SQ” line
  • 3922 - 39SQ - date
  • 3923 - 38SQW - day/date