The Bo-Uk-FI 23885 Blindfluguhr (blind-flight or instrumental flight) clock was used in the Messerschmitt ME BF 109 and specifically designed for low visibility flight. Although simple in appearance, it provided the pilot will all the necessary information for flying in more challenging conditions. The flight time was registered at take off by selecting the hour with the rotating bezel. The chronograph or timer had multiple uses, including use for the approach to land with no visibility, calculating airspeed and keeping track on fuel usage. The minute register records up to 15 minutes, the approximate amount of flying time left after the 'low fuel' warning lamp illuminates. This clock was an essential piece of kit for the pilots, who were instructed to remove it if they had time after an emergency landing, before leaving the wreckage. During the time the Me109 was in production, 5 models of this clock were used, some with brass bezels, others with bakelite. Fully wound, the Bo UK 1 has power for 36 hours.
Watch a video of this clock in its working order