What was found
(CAN) FLIGHT CREW ADVISED COMPLETE DEPLETION OF FLIGHT CREW OXYGEN WHILE ENROUTE/OVER ICELAND. IN CONSULTATION WITH THE DUTY PILOT/FLEET MANAGER AND FLIGHT DISPATCH THE FLIGHT WAS RECOMMENDED TO CONTINUE AS LONG AS THE ACFT PRESSURIZATION WAS NORMAL AND THE SPARE CABIN OXYGEN WAS BROUGHT TO THE FLIGHT DECK FOR THE REMAINDER OF THE FLIGHT AS A PRECAUTION. REPLACED CREW O2 IAW AMM TASK 35-11-41-400 VALVE WITNESS WIRED OPEN FOUND 2ND OBS MASK LEAKING BECAUSE WAS NOT INSTALLED CORRECTLY, REINSTALLED 2ND OBS MASK TESTED, SERVICEABLE.