Navigation wristwatches made by Walter Storz (Stowa), Lacher & Co. (Laco), IWC, Lange & Söhne and Wempe were horological specialties. They were regulated as navigation chronometers and tested, piece-by-piece, by the chronometer department in Gesundbrunnen near Glashütte. The aircraft navigators wore these watches with long leather straps above the sleeve.
For a detailed note on such aviator's watches see lot 399 in this auction.
The models are described and illustrated in Military Timepieces by Konrad Knirim, pp. 344 - 351.