If you have Donald Nijboer’s book “ COCKPIT” you can find the instrument clearly in several of the photos Oxygen Pressure Gauge Type K-1 WWII Surplus NOS in sealed box Dated Oct 1943, Hard to find item Gauge was mounted at each crew position on the Bombers of WWII and in the cockpit of every WWII fighter, gauge would indicate O2 left in the pressure tank. The one you win will be sealed in the original box.