B-Uhr project: the history of Observation watches | part 3

The Big Five

Observation wristwatches type A. Lange & Söhne

In 1935, A. Lange & Söhne received the first order from the German Wehrmacht to develop a large wristwatch for the Air Force. This was done on the basis of a hand-wound caliber, the history of which went back to the 1920s. The 17-stone version 48.1 with a diameter of 48 millimeters and a height of 8.75 millimeters found its way into the wristwatch case. Its features included a balance frequency of 2.5 Hertz, an indirectly driven central second, a hand setting mechanism operated via the crown and a balance cock with a patented spiral stud fastening. The second stop was based on a patented development by the Junghans brothers, Schramberg. The steel anchor, which was stored under a separate clamp, was balanced. Depending on the version, a Guillaume compensation balance or a slotted nickel steel balance was used. And always together with a Breguet hairspring. Some of the Rücker had a gooseneck fine adjustment. A Maltese cross position was used to regulate the tension spring torque.

Most of the models were available in versions with two differently designed dials: One with a large minute track and a small internal hour circle. The hour hand was correspondingly short here. The other version had large hour digits right next to the 5-minute indexes.

The Waffen-SS received a special model with Roman hours and Arabic minutes and seconds. The latter were also done in mirror writing so that the seconds could be read off in certain cases using a mirror.
In addition to these standardized pilot observation watches, significantly rarer models with an arc degree dial were created for navigation purposes. The hour hand moved through 360 degrees of arc within 24 hours, analogous to the rotation of the earth.

The design of the dial, including that of the zero point, was based on the respective requirement profile.

The large pilot’s watch from IWC

At the request of the German Air Force, the Schaffhausen International Watch Co. also developed a professional pilot’s watch at the beginning of the Second World War. This model had effective protection against magnetic fields because the technicians had surrounded the movement with a dial, movement ring and inner base made of particularly conductive soft iron. IWC equipped its model with the tried and tested pocket watch caliber 52 SC (19 lines, diameter 43.15 mm, height 6.5 mm, 16 jewels), where SC stands for center seconds.

The time was divided by a bimetallic compensation rest with a Breguet hairspring. The regulator had a gooseneck fine adjustment. A Geneva cross position mounted in the barrel lid was used to regulate the torque.

IWC produced a total of 1,200 of this hand-wound movement between 1940 and 1945. However, only a small part of it ended up in the said pilot’s wristwatches. The company also equipped deck watches (pocket watches) and civilian pocket watches with them. All military models had the same case and movement numbers. For security reasons, the case numbers were used a second time on civilian timepieces. Because the recipients of the pilot’s and observation watches only appear in encrypted form in the IWC records, they can no longer be identified today.

Wempe type observation wristwatch

Wempe Chronometerwerke, founded in Hamburg in 1878, used the 18½-line caliber 36 from the Swiss manufacturer von Thommen in Waldenburg for their own observation wristwatches. The bridge movement has the following structural features: diameter 41.85 mm, 15 jewels, indirect center seconds, Glucydur screw balance with Breguet hairspring, fine adjustment device with a Thommen-typical worm disk and a brake spring for the balance wheel that is coupled to the pointer setting device.

Stowa type observation wristwatch

The Pforzheim-based establishment Walter Storz (Stowa) also obtained the raw works for his observation wristwatches from the Swiss Confederation. The Ebauches supplier Unitas goes back to the Fabrique d’horlogerie Auguste Reymond (ARSA) founded by Auguste Reymond in Tramelan (Canton Bern) in 1898. In 1926, the company acquired the Unitas Watch Co., Tramelan, whose factory building it converted specifically for the manufacture of raw movements. In 1932, the Ebauches Unitas department came under the umbrella of the Rohwerkeholding Ebauches S.A., while the Arsa watch production continued to be independent.

The 20-stone Stowa-Unitas caliber with a diameter of 46.5 mm was the only one with a Geneva cut as the surface decoration for the bridges and cocks. Technically, it has a slotted Guillaume balance wheel, Breguet hairspring and an elegant gooseneck fine adjustment for the regulator. The absolutely necessary balance stop takes place with the help of a brake spring, coupled with the pointer setting device

Lacher & Co. (Laco) observation wristwatch

In addition to A. Lange & Söhne, only the watch factory Lacher & Co. (Laco) founded in Pforzheim in 1925 used a caliber of German provenance. This came from the in-house raw work manufacture Durowe (Deutsche Uhren Rohwerke). The gold-plated caliber D 5 has a diameter of 49.4 millimeters and 22 functional stones.

In addition to the usual bearing stones, the escape wheel also has cap stones to limit the vertical play of the shaft. All perforated stones had olive holes. A slotted Guillaume balance, 22 mm in diameter, with regulating screws and a Breguet hairspring serves as the regulator. Here, too, the balance is stopped by a brake spring. In the lid of the barrel there is a Geneva cross position to limit the torque.

The observation wristwatches from A. Lange & Söhne and IWC enjoy the highest reputation among collectors. The prices are correspondingly high. Which is not to say that the copies of the other types are cheap. Either way, the military tradition of these timepieces comes at a price.

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Gisbert L. Brunner, born in 1947, has been working on watches, pendulum clocks and other precision timepieces since 1964. During the quartz clock crisis of the 1970s, his love for the apparently dying-out mechanical timepieces grew. His passion as a hobby collector eventually led to the first newspaper articles in the early 1980s and later to the by now more than 20 books on the topic.
Amongst others, Brunner works for magazines such as Chronos, Chronos Japan, Ganz Europa, Handelszeitung, Prestige, Terra Mater, GQ and ZEIT Magazin. He also shares his expertise on Focus Online. Together with a partner, he founded the Internet platform www.uhrenkosmos.com in 2018. After the successful Watch Book I (2015) and Watch Book II (2016), the teNeues publishing house published the Watch Book Rolex, written by Gisbert L. Brunner, in June 2017. The book has appeared in German, English and French and has already been reprinted several times due to high international demand.