The author used an x-ray element analyzer to determine the composition of a Seiko chronometer hairspring, finding that the composition was that of elinvar, not coelinvar. Jiro Sato described the coelinvar as having a higher modulus of elasticity than elinvar, and it is known that even elinvar is very brittle and hard to work with.⁶ However, they could not manufacture a perfect helical coil-spring using coelinvar⁶ because coelinvar (then) was too difficult to manipulate to manufacture the complicated helical coil⁶ (after World War II, Seiko employed coelinvar for their watch coil spring).

Mr. Sato,⁶ Daini-Seiko-sha engineer, and former Naval Commander Sugiyama³ state that preparation for mass production began in 1941, and was underway in October 1942. Somewhat less than 600 timepieces were made, including some nearly finished but not used, and supplied for use in the warships of the Imperial Navy of Japan. How good were they?

The Office for Naval Organization was responsible for ordering and approving the chronometers. Daini-Seiko-sha chief engineers also inspected the finished timepieces. Accuracy testing was done by using the pulse rate from Japan radio. The chronometers had a break-circuit for pulse output, (See outlined area in Figure 6.), and this output was compared with the radio pulse. All of the chronometers were adjusted to a daily rate accuracy of plus/minus 1-second / day, and achieved less than 0.5 seconds / day deviation. They met the naval standard (Table 1). Some of the clocks performed even better, with a daily rate deviation of plus/minus 0.1 seconds. Thus, the chronometers were built to a very high level of precision, and were met with great enthusiasm by naval high command.^7,8

Conclusion

The short-lived history of the Seiko-sha two-day marine chronometer has been described. Daini-Seiko-sha produced less than 600 of these excellent timepieces during the pressures of World War II. It was an almost exact copy of the Swiss Ulysse Nardin chronometer, successfully built by the engineers of Daini-Seiko-sha and others through an all-out effort to surmount many obstacles. Through their efforts, they achieved a higher level of accuracy than simply copying would have produced, and in the process, undoubtedly sowed the technology seeds that later resulted in the highly accurate post-war Seiko watches. Very few Seiko-sha chronometers survive due to the almost total destruction of the Japanese Navy during World War II.

Acknowledgment

Grateful thanks go to: Mr. Taro Yasukawa (former Naval Lieutenant) who supplied valuable naval documents; Kyouji Sugiyama (former naval assistant engineer); Masahito Yoshino (Seiko-Epson Co. Ltd.); Ryouchi Sugiyama (former Naval Commander) and Dr. Jerome F. Walker for their great assistance. Special thanks to Doug Cowan, the first vice president of NAWCC, for his help in the editing of the paper.

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About the Author

For Professor Dr. T. Haruyama, horology is his hobby, not his profession. He enjoys collecting ships clocks, marine chronometers and pocket watches, especially Japanese chronometers and foreign chronometers retailed in Japan during the Meiji era (1868-1912) and Taisho era (1912-1926).

Endnotes

1. Seiko was established in 1881 by Kintarou Hattori as Hattori Watch and Jeweler in Ginza, Tokyo. In 1892, a manufacturing division was separately established as Seiko-sha. In 1917, Hattori Watch and Jeweler was organized as a company with the two firms. The Seiko brand was first used on watches in 1924. In the course of 1937-1942, the group was separated into three companies: Hattori Watch and Jeweler, Daini-Seiko-sha and Yamato engineering. Daini-Seiko-sha and Yamato engineering mainly produced watches. The Seiko group currently consists of five independent corporations: Seiko Epson (watches, computers, LC, quartz, etc.), Seiko Instruments (watches, electronics devices, measuring instruments, etc.), Seiko (watches and clocks), Seiko clock (clocks) and Seiko precision (watches and clocks). Incidentally, the retail building of Hattori Watch and Jeweler was occupied by GHQ (General Headquarters of US occupation) as the Tokyo PX store after WWII from 1945 to 1952. The present name of the building is Wako, which is owned by Seiko Co. Ltd., and it is a high-class department store.

2. Hattori special instruments catalogue, vol. 10, p. 267, (1936).

3. The author interviewed Ryouichi Sugiyama (former Naval Commander) in 1997.

4. Professor Hakar Masumoto (Imperial University of Tohoku) is well known as an inventor of coelinvar. He was decorated by the First Order of Merit in 1966.

5. Hakar Maumoto, Journal of Metallurgical Society of Japan, 2(4), 141-146 (1938). Hakar Masumoto, Journal of Metallurgical Society of Japan, 8, 513-516 (1944).

6. Jiro Satoh was an engineer of Daini-Seiko-sha and was in charge of development of the full-size marine chronometer during WWII. His remembrance regarding the Seiko marine chronometer was described in Jiro Satoh, Memoirs—history of watch and clock engineering. Eds. by Seiko Co. Ltd. and Japanese managing history laboratory (1981).

7. Seiko-sha Shiwa (History of Seiko Co.), pp. 323-324, Ed. by M. Hirano (1968), Seiko-sha, Tokyo.

8. Taro Yasukawa was a naval engineering officer (Lieutenant) in the Naval Navigation Laboratory. The author interviewed Yasukawa in 1996 and in 1997.