Time-to-Go Indicator, Type Mk I, for B-52 Bombing Navigational Computer BRANE

Here is what we've been able to piece together from our research on this Cold War-era Time-to-Go Indicator.  Interested collectors may want to verify independently:

It seems to have been a component of the IBM Type Mk I Bombing Navigational Computer, aka the BRANE (Bombing Radar And Navigation Equipment) system, used in the US Air Force SAC B-52 Stratofortress bomber, likely versions E or F based upon the date stamp on the indicator of 1958.  This indicator would have appeared at the station of the Radar Navigator (Bombardier), below the flight deck.  

The Time-to-Go Indicator displayed the flight time remaining to reach the aircraft's destination, up to 360 seconds, as determined by the bombing navigational computer after data entry by the Radar Navigator.  

Measures 3.25 inches diameter and ~6 inches deep. It is in exceptional condition for its age.