As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FO SIDE O2 MASK RED TAB BROKE OFF. SWAPPED F/O O2 MASK WITH OBSERVERS O2 MASK. PERFORMED OPS & LEAK CHECK OF CREW OXYGEN SYSTEM & CREW O2 MASK MICROPHONE IAW AMM 35-10-00 & 23-51-00 OPS CHECK GOOD. REMOVE OBSERVER O2 FULL FACE MASK IAW AMM 35-11-12-000-801, INSTALLED NEW FULL FACE MASK IAW 001714121 35-11-12-400-801. LEAK TEST WAS PERFORMED IAW 35-10-00-790-801, MIC TEST WAS PERFORM.