What was found
OXYGEN BOTTLE RECEIVED FROM REPAIR SHOP FOR FITMENT TO AIRCRAFT. ON FITMENT OF OXYGEN BOTTLE ASSY DURING 30 MINUTE LEAK TEST IAW MM, REV 12, 35-10-00, REV 8, 6, B 11A. LEAK DETECTED FROM PRESSURE REGULATOR ON/OFF VALVE. PART REMOVED FROM AIRCRAFT AND RETURNED FOR REPAIR. COPY OF INCOMING AIRWORTHINESS APPROVAL TAG FAA 8310.3, PN, SO32073077-1.000.