Aircraft Clock, Jaeger LeCoultre A-10 Chronoflite Elapsed Time Chronograph, US Navy
This is a WWII-era 24-hour 8-Day Aircraft Clock, USN stock number R88-C-570-10, made by Jaeger for use in aircraft of the US Navy, such as the PBY Catalina, TBM Avenger, and F4U Corsair. Known as the Jaeger LeCoultre A-10 Chronoflite Elapsed Time Clock, this version has the functions of Elapsed Time, Center Seconds Chronograph, and Civil Date Function.
A colleague offers this explanation of its operation:
Push the left button. When the top flag is red, and the bottom flag is red, the top timer is running (minutes, hours). To pause the top timer rotate the center knob until the bottom flag is white. To resume the top timer, rotate the center knob until the bottom flag is red again.
When you’re done with the top timer press the left button again. The top flag will turn red and white (stopped). Then if you press the left button again it will reset.
The cool thing is that if you’re paused and you reset the top timer with the left button the center knob will actually move so that the bottom flag is red (so that the timer actually starts and isn’t paused the next time you press the left button).