With the outbreak of World War II, the Reichsluftfahrtministerium (Reichsfuhr Aviation Ministry) recognized the need for an efficient aviation clock (Beobachtungsuhr or B-Uhr) to be used by the aircraft’s navigator, to assist crews in long-range bombing missions. These models were also worn by aircraft pilots, who needed wristwatches that could be read with precision and immediacy when both hands were engaged in flying the plane and large so comfortable to handle with gloves

This model was given the classification number FL 23883 of the Reichsluftfahrtministerium. This number appears on all Luftwaffe watches of this model.
Inside the case are printed the type of watch, the device and movement number and the warehouse number