Military Timepieces:
Japanese Military Timepieces in WWII.

by Konrad Knirim,  published in the
Horological Journal of the British Horological Institut Dec. 2001
NAWCC Bulletin No. 339 August 2002

Introduction
It is difficult for a European collector to deal with a topic such as this. Firstly there is to a dearth of historical artifacts and collectors pieces in Europe relating to this era. Secondly, because the Japanese script and the countries cultural background is so different to that of Europe. The author would like to thank those who made the completion of this difficult task possible. A crucial role was played by Don Wright of Tulsa/Oklahoma, who made his collection available to be photographed by the author. Some of the pictures used were by Kesaharu Imai, taken from WPP (World Photo Press) publications. Also, some of the photos used were by Steffen Röhner. The author discovered several photos depicting Kamikaze pilots wearing watches and clocks hung around their necks at a special exhibition by the Royal Navy at its Fleet Air Arm Museum in Yeovilton, Somerset, England. Tadashi Noda of WPP helped in identifying and deciphering the markings. Unfortunately, it was not possible to explain how the Japanese Army and Navy acquired and distributed the timepieces in question, as Japanese air power was just a component of the Army and Navy. It was also not possible to properly outline the origins of these watches in this article. For example, it is difficult to know just how much they were copied from Swiss models. It is a fact that from the 1920’s onwards, Japan was working to develop navigational timepieces of its own. However all prototypes were destroyed by fire as this process was still ongoing. This meant that the model built along the lines of Ulysse Nardin’s chronometer became the most important and predominant model to be used by the Japanese.

As with most present day watch producers, watch manufacturer Seiko (see box), did not see a decline after the end of WWII. and wartime equipment supply manufacture. An overly narrow focus on Seiko’s aviator watch’s image was eventually to damage their reputation. It has long been recognized that timekeeping plays an important role in both military and civilian life. Countries such as England, America, Germany and Japan, had their own military timepieces, all comparatively similar in design. This article will deal with some such Japanese military timepieces. As items of this type are seldom to be found in European collections, this report can in no way be seen as authoritative. There have also been only a few reports on Japanese military clocks up until now. The American S.M.H. or ‘Society of Military Horologists’, Chapter 143 of the NAWCC, have so far published two black and white reports. The first report from 1993, ‘Japanese Aviation Timepieces’ by Gary D. Nila, is about watches of the Japanese air forces. The second report from 1997 by John Mitchell of England, is an entirely photographic piece entitled ‘A Collection of WW II. Japanese Military Timepieces’. For the most part these articles showed variants of the watches dealt with in this article. There are variations in details such as casing material, the presence of a twisting dial-face, or the markings such as the insignias of various branches of the military. This is probably the first time that a ship’s chronometer and wall clock has been dealt with in this context.

Types of Clocks dealt with in this Article
- Ship’s Chronometers and
- Ship’s Wall clocks
- Specialized Timepieces
- Aircraft Clocks
- Commando Pocketwatches
- Artillery Chronographs and Stopwatches
- Wristwatches

Manufacturers:
Almost every Japanese military timepiece seen to date has carried the mark of watch manufacturer ‘Seikosha’ or ‘K. Hattori’, the forerunners of the modern day Seiko Co. Ltd. Ginza Tokyo, Japan. The mark of another producer, Aiti Tokei Denki KK, appeared on a ship’s clock and also on a timed detonator. Swiss and German products, in particular chronographs and wristwatches, were undoubtedly worn by Japanese flight crews as well.

Ship’s Chronometers
Description: The Seikosha chronometer shown here, no. V-872, in a three part wooden casing with spyglass, has the same numbers on the movement, dial and case. The movement is excellent workmanship, with chronometer escapement and fusée. It was copied from, or licensed to be built by, Ulysse Nardin. The Kanji and Katakana characters for ‘Seiko, Meridian’ are marked on dial above the middle axle. In the second-circle is the number V-872 in Latin characters. The small inscription at the bottom and the dial face edge cannot as yet be deciphered. An electrical second contact needed to control slave clocks, as well as other signals, was conducted through an inner and outer plug.

Ship’s Wall Clocks
Ship’s wall clocks with one-week movements, such as various versions by Seikosha, are relatively common. Take for example, the piece numbered 11227. The inscription on the dial-face says ‘One-Week Movement’. The casing has been numbered ‘A831’. Astonishingly, the ship’s wall-clock, number 104, from Aititokei Denki KK. Nagoya, Japan, only had a one-day movement. The inscription on the dial-face reads: ‘One-Day Movement Mod. 1’. On the casing edge is the Navy anchor and the number ‘B238’. A small yet unusual detail is the left-sided winder.

Specialized Timepieces
The Japanese military machine, with its many and varied functions, needed a large amount of timekeepers under the broad heading of ‘displaying the time’. The more unusual timepieces included a timed detonator setup, a dark room clock and a surveillance control clock. It is not clear what the Navy timed detonator number 1235 by Aiti Tokei Denki Co. Ltd. was used for. It could possibly have been built into torpedoes. However, its 36-hour operating time meant more that it was more likely to have been fitted in sea mines. Many photo-laboratories equipped with dark rooms were set up to process the large amount of photographic material gathered on targets etc. The inscription on the case and type-plate reads: ‘Dark room clock’, number 1270. The five-pointed star identifies it as belonging to the Japanese Army. The surveillance of military objects needed to be precisely controlled and time-checked. Control books and surveillance clocks were used for this purpose. Displayed here is piece number 5756 from K. Hattori and Co. Ltd. Ginza, Tokyo. The dial signature consists of the letters ‘KH’ in a rhombus. The piece is identical to the one made by Bürk of Schwenningen, used by the German Kriegsmarine. The piece’s cover illustrates that many such clocks came into the hands of collectors as war booty. The following message is scratched onto the cover: ‘Taken from Yokusuka Naval Air Base Japan, Sept. 26. 1945, R. H. Gerber.

Aircraft Clocks
Description: manufactured by Seikosha, pre-1940 brass casing and hinges, post-1940 patent metal twisting bevel with red, blue or green arrows for time-marking, large Arabic radium illuminated digits (radioactive), flange with four holes allowing the clock to be fitted to aircraft instrument panels, a large brass knob (up to 1949) or plastic knob (after 1940) which was pulled out to set the clock, ca. 7.5 cm diameter. Such clocks were fitted in the instrument panels of all Japanese aircraft. All clocks originally had the manufacturer’s type-plate. In some cases the specifications can be translated as ‘Type 100 Clock’ The Army air force used some clock type-plate showing the Army star alongside various quality control markings. It is likely that examples also exist which bear the Navy anchor. ‘The Type 0’ marking probably indicates the Navy. This clock was sometimes called the ‘Zero Clock’, after Mitsubishi’s ‘Zero’ fighter-air craft. Clocks with brass casings date from 1936 at the earliest, and from 1939 at the latest. They are heavier and have a dark, golden yellow sheen. They were coated with a black paint that can be scraped off easily. The winding knob, as well as the type-plate, were also made from brass. As before, all the early versions have the Army stamp. Post-1940 clocks have aluminum casings with a plastic winding knob and an aluminum type-plate. They were varnished with a matte black paint. Under the paint the housing has a matte gray metal surface. A length of parachute silk was often threaded through the fastening holes. The pilot would have worn the clock around his neck allowing him to easily read the time on the clock around his neck. The photographs show Navy air force kamikaze pilots before embarking on their last mission. They are wearing clocks around their neck. Some of the winders are pointing upwards, some downwards. To the observer, all the clocks are facing the wrong way. According to Navy air force pilots, clocks were not issued, but privately purchased. They were evidently expensive luxury items. After completing their training, many Navy air force pilots received clocks as gifts from friends or relatives. However, most Navy pilots reported that they never had a watch. Obviously, the practices of Navy and Army pilots were very different. It is also important to note that taking a clock from an aircraft without permission was considered to be theft. Anyone caught doing so was severely punished.

Commando’s Watches
The dial of Seikosha’s large pocket watch has a typical navigation-clock design. Despite the fact that it had a 65 mm diameter, the piece had a completely normal pocketwatch movement. It is a 17½ inch movement with a 36-hour operating duration, seven jewels and a screwed-bimetal-movement with Breguet spiral. However, it does not meet the precision operating demands of a navigation watch.

Pocket Watches
Description: manufactured by Seikosha, 36 hour operating duration, 17½ inch, here with 15 jewels, bi-metal movement with Breguet spiral, nickle or chrome plated housing, Arabic numerals, illuminating points on each digit, ca. 2½ inches tall, smoked glass. The dial is white or black, the digits are large, and next to them are small illuminating dots. There are various different second indicators and scales. A chain or a strap made from parachute silk allowed the watch to be worn around the neck. Some naval inspection markings, as well as the aviator’s initials and personal engravings, are to be found on the back of the watch.

Artillery Chronographs
When dealing with Japanese military timepieces, one regularly encounters Seikosha artillery chronographs. These pieces were used to measure all types of measurement intervals. Here is an example from the Navy: ‘Second-Clock, Type 1, Class 2’. Engraved on the reverse side of the watch is the number 117 and a symbol in a circle that means ‘water’. This indicates that the watch was used on a torpedo boat or submarine. The Swiss-made Moeries pocket chronograph was used by the Japanese aviation corps. It is marked ‘Type 89’, and on the reverse side is ‘Air Force Second-Clock Type 1’. It was fitted as part of an aircraft’s onboard camera setup.

Stopwatches
As with chronographs, stopwatches were used to measure time intervals in many different fields. Stopwatches were most commonly used for artillery range finding. The stopwatch measured the time difference between the flash and the bang produced by an artillery discharge. The difference in velocity between light (300,000 km/sec), and sound (300 m/sec), was used to calculate a target’s distance. The word ‘Phonotelemeter’ in Latin characters was sometimes printed on the dials of Seikosha stopwatches. ‘Acoustic Distance Measurer’ was sometimes engraved on the covers in Kanji. Stopwatches were also used for long-range targeting, or on board torpedo boats and submarines to measure torpedo running-time.

The Oversized Aviator’s Watch
Manufacturer: Seikosha, movement: 17 jewel bimetal movement with Breguet spiral, indirect central second indicator, housing: nickel coated, twisting bevel, Arabic numerals with enlarged 3,6,9 and 12, self-illuminating digits on a black face, nearly 50 mm in diameter. This watch had two roughly 15 cm long, broad leather straps. The straps were long enough to enable the pilot to wear the watch on his arm over his thick flying jacket. As before, these watches were not issued by the military but were privately owned. The central second movement is the same as that of the aircraft clock. It also moves at the same basis caliber as the pocket watch with the small second hand. It is not shock-proofed. The large winding crown allowed the watch to be wound or set while wearing gloves. The watch did not bear the star or anchor markings of Japan’s two military branches. However, photographs conclusively show that both Navy and Army pilots made use of this watch.

The Wristwatches
There were watches of this type, with and without twisting bevels, and with differing casings. For the most part, the dial faces are inscribed with the Army star or the Navy anchor, as well as the ‘Seiko’ brand name. The digits were written in Arabic numerals on all the watches. The Japanese numerals were very often changed during marking.

Suggested Literarure:
Kesaharu Imai, Military Watch Encyclopedia, Green Arrow, ISBN: 4-7663-3185-0

Kesaharu Imai, Zeitschrift ‘mono’ Nr. 177 1990

Gary D. Nila: ‘Japanese Aviation Timepieces’ ‘Society of Military Horologists’ 1993

John. Mitchel, ‘A Collection of WW II. Japanese Military Timepieces’ ‘Society of Military Horologists’ 1997.

Marvin E. Whitney, Military Time Pieces, American Watchmakers,
ISBN: 0-918845-14-9.