The Origins of the German B-Uhr watch (observation watch)
As Germany prepared for war the German Ministry of Aviation responsible for aircraft development understood that being able to coordinate mass attacks combined with the use of cutting edge weaponry would ensure overwhelming results in their war efforts.
As timing was a key element to unmatched precision, the German Ministry of Aviation sought a commensurate time piece for its bomber navigators, the responsibility to produce accurate and usable timepieces with which to control the war was given to five manufacturers: A. Lange & Sohne, IWC, Wempe, Stowa and Laco.
The B-Uhr watches (B-Uhr in german stands for Beobachtungsuhr or observation watch in english) were 55mm big to accommodated large hand-wound movements typically used in pocket watches, black dials with white Arabic numerals and flame-blued sword hands covered in luminous material further aided the task of precise reading.
There were two variations of the B-Uhr, the A and B-Dials.
The A dial is a much cleaner design with large 1 to 11 numerical, all numerical markers were also filled with luminous material.
The B dial was a bit more complicated as it showed 5 to 55 minutes markers on the outer rim and a downsize inner circle with the typical 1 to 12 numerical hour marks similar to the A dial. Compared to the A dial, the B dial had a much shorter hour hand that moved in the inner circle of the dial.
B-Dials also featured a unique triangle mark at the 12 o’clock position designed for the upward orientation of the dial of the watch during flight
In order to be able to synchronize the time of several watches and coordinate war operations the movements were capable of stopping the central seconds hand by pulling the crown (hacking), oversized diamond or onion crowns could be operated with gloves on the hand, and a very long double-riveted leather strap to go over the leather flight jacket held the B-Uhr in place.
Wempe and Stowa used Swiss movements; Wempe used the Thommen cal. 31, Stowa used the Unitas cal. 2812. Lange used its big cal. 48 and then its cal. 48.1, and Laco used its (Durowe) cal. 5 – the only two companies to use in-house German movements.
All the watches were marked FL23883, FL meaning fliegnummer (flying number), 23 designated it as a device for flight monitoring and the 883 was assigned by the Deutsche Versuchsanstalt für Luftfahrt (German Testing Office for Aeronautics).
These watches remind us of a horrific time in human history but they also capture a desire to make the best possible timepieces to do a much needed job. The B-Uhr design is a good example of form following function and one that attracts many watch-enthusiasts to this day.
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