Seiko ultra-thin quartz
Seiko produced the first quartz watch for sale to the public in 1969, the groundbreaking Seiko Astron. Its Cal. 35SQ evolved rapidly over the few years it was produced, but the successor movement, Cal. 38, set the template for future quartz movements, with a stepper motor and integrated circuit divider on its introduction in 1972. By the mid-1970s, the two Seiko factories were rapidly iterating, releasing a new movement nearly every year throughout the decade.
Seiko produced the first movement compact enough for a ladies watch, Cal. 03, in 1972, and replaced this in 1974 with the more robust Cal. 41. Although not a thin movement at nearly 4 mm thick, it nevertheless showed that quartz technology could be miniaturized. Mass-produced miniature 32 KHz tuning fork quartz crystals, CMOS ICs, compact stepper motors, and advanced batteries were all rapidly advancing and coming to production.
Citizen and Seiko initiated a so-called “thin watch war” in 1978, with Citizen first to market with the Quartz 790, also called the Exceed Gold. The watch was moderately thin at 4.1 mm, but the movement, Cal. 790 was remarkable. It measured just 0.98 mm thick, though the battery and hand set more than doubled this. The watch was nevertheless impressive, and Seiko (and the Swiss Delirium project) set about beating their record.
Seiko was next to market, announcing the ultra-thin Cal. 9320 on July 20, 1978. It measured 0.90 mm thick, setting a new record just a few months after Citizen, and was featured in an ultra-thin watch that measured just 2.5 mm. These caused an international stir, with a high-profile release at famed New York jeweler Tiffany & Co. at a price of $5,000. For the first time, a Japanese watch was the high-dollar focus of American tastes. Sold under the new Credor label in Japan, the HGY614 (9320-7000) feature Seiko branding on the dial and can be seen as a stepping stone between the Grand Seiko lines of the 1960s and Credor and Grand Seiko of the 1990s and beyond.
These releases from Japan caused great concern for the North American Watch Company (NAWC), which had been the leader in high-end ultra-thin watches in America with the Piaget brand. They demanded that Ebauches SA produce a thinner watch, leading to the creation of the Delirium, which was sold in the United States under the Concord brand. They announced their 1.98 mm watch on January 12, 1979, which featured a remarkable 1.1 mm battery from Renata.
Later that year, ETA and Concord announced the Delirium II which, at just 1.43 mm, was impractical for everyday wear but nevertheless set a record. The Delirium movement was integrated with the case, however, making comparison of movement size difficult. Seiko responded to the Delirium with an even thinner watch to house Cal. 9320. The Seiko/Credor 9320-400x was just 1.79 mm thick, but it arrived a few months after the thinner Delirium II. Both were impractical watches designed for collectors and museums, and both are quite rare to this day. The ultimate expression of this impractical line was the Delirium IV, which appeared in December 1980. The entire watch was 0.98 mm thick, with a special battery and engraved crystal discs rather than hands.
Both Citizen and Seiko also created more practical versions of their ultra-thin watch movements, and these sold for far less than the ultra-thin leaders. Daini Seikosha bested rival Suwa's movement by 0.01 mm with their 1980 Cal. 6720, which was also smaller in diameter. At 18x13x0.89 mm, it would become one of the smallest movements ever made. Their Cal. 2F family of 1983 was also impressively small, measuring 15.55 mm diameter and 1.39 mm thick. Suwa released another family of ultra-compact movements in 1984. Their Cal. 5A family measured 1.3 mm thick and was used in watches from Seiko's recently-acquired Lassale brand as well as Credor and Seiko.
The final ultra-thin watch movement from Seiko, and still the world's thinnest movement, appeared in 1989, fittingly in a watch that celebrated the 20th anniversary of the Seiko Astron. The SCQX 20th Anniversary watch was a wearable 3.36 mm thin and houses the remarkable 0.85 mm Cal. 9A85A. The movement was created by Suwa Seikosha (now called Seiko Epson) and was finished and decorated in high-end style despite being housed in a closed-back watch. The gold Anniversary watch sold for over 1 million Yen, more than twice as much as contemporary gold Seiko watches, and remains a collectible.