The B-Uhr
The German air force navigator’s watch of the Second World War: a 55 mm instrument built to specification Fl 23883 by A. Lange & Söhne, Wempe, Laco, Stowa and IWC, whose two dial patterns still shape the pilot’s watch.
Made From 1940 (specification drafted from 1935, by one account), By A. Lange & Söhne, Wempe, Laco, Stowa, IWC
Companies A. Lange & Söhne, IWC Schaffhausen, Laco, Stowa
In the histories German watchmaking, Watches go to war
The specification
The Beobachtungsuhr, observation watch, was the navigator's watch of the German air force. The Reich Aviation Ministry (RLM) set its requirements in specification Fl 23883.1, 2, 3
Worn & Wound says the ministry drafted the specification in 1935, at first with an hour-angle display like Lindbergh's Longines; the German Wikipedia says the makers were ordered to start production in 1940.1, 2
The specification called for a 55 mm case, a large onion crown that could be turned in gloves, a black dial with luminous hands and a triangle at twelve, and seconds that stopped when the crown was pulled.1, 2, 3
It was worn over the flying suit on a long strap, and had to run precisely and be read at a glance.2, 4
It was used with an octant to fix the aircraft's position from the sun or stars. The German Wikipedia calls it a misconception that pilots wore it: navigators did, while pilots wore chronographs such as Hanhart's.1, 7
Five makers
Five firms made it: A. Lange & Söhne and Wempe, Lacher & Co. (Laco) and Walter Storz (Stowa) in Pforzheim, and IWC in Schaffhausen, in Switzerland.1, 2, 8
Movements, by Worn & Wound's list: Lange calibre 48 and 48.1, Laco Durowe calibre 5, Wempe Thommen calibre 31, Stowa Unitas 2812, IWC 52 T.S.C.; the German Wikipedia also gives Lange calibre 48 and a Thommen movement for Wempe.1, 2, 9
Wempe bought the Hamburg Chronometerwerke in 1938 and helped Lange and Laco meet demand; Lange also sent movements and cases to outside firms for assembly.2, 10
Two dials
Two dial patterns exist. Baumuster A has hours 1 to 11 and a triangle with two dots at twelve; Baumuster B has a large minute ring outside and the hours on a small inner ring. Worn & Wound dates A to 1939 and B to 1941; other accounts put B around 1942.1, 2, 3
The German Wikipedia records that each case carried the Fl number on the case edge and back with maker, type, device number and movement designation.1
Afterwards
Stowa reissued its B-Uhr in 1997 and Laco recreated its own in 2000; both build most of their pilot's watches on the two patterns today.9, 11
Where the B-Uhr leads
- Made by, CompanyA. Lange & Söhne
One of the five makers of the observation watch.1, 2
- Made by, CompanyIWC Schaffhausen
The Swiss maker among the five builders of the German observation watch.1, 2
- Made by, CompanyLaco
Lacher & Co. built observation watches on Durowe movements.2, 11
- Made by, CompanyStowa
Walter Storz built observation watches with the Unitas 2812 from 1940.2, 9
- Part of, HistoryGerman watchmaking
The air force navigator’s watch made by Laco, Stowa and A. Lange & Söhne in the Second World War.1, 2, 3
- Part of, HistoryWatches go to war
Germany’s navigator’s watch, built by five firms to one specification.1, 2
- See also, PlaceSchaffhausen
One of the five B-Uhr makers worked here: IWC, with its calibre 52 T.S.C.1, 2
- See also, TraditionPilot’s watches
Its dial patterns remain the basis of German pilot's watches.9, 11
- See also, EventThe Second World War
The German air ministry’s observation watch, built by five firms.1, 2
Facts and sources
- Made
- From 1940 (specification drafted from 1935, by one account)1, 2
- Makers
- A. Lange & Söhne, Wempe, Laco, Stowa, IWC1, 2, 3
- Specification
- Fl 23883, engraved on the case1, 2
Sources
- 1
- 2
Military Watches of the World: Germany Part 1 (opens in a new tab)
- 3
The History of the Pilot Watch Part Five: B-Uhr (opens in a new tab)
- 4
- 5
- 6
- 7
Bundesarchiv Bild 146-1986-101-29, Standortbestimmung im Flugzeug (opens in a new tab)
- 8
- 9
- 10
- 11
Sources read November 11, 2026.