Oxygen Flow "Blinker" Indicator, PN 1506523 AN-6029-1

This is a WWII-era Oxygen Flow Indicator "Blinker" made by Delco PN 1506523. This indicator was used across nearly all aircraft of the US Army Air Force and US Navy. When the oxygen system was switched on the oxygen flow caused the center 'eyeball' to open and close, or blink, thereby confirming to the crewman that the oxygen supply was indeed flowing. 

This indicator is in exceptional condition for its age.  The glass and case are intact and clean. Measures ~2.5 in. square by 2.5 in. deep.