As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A, AIR TURNBACK 0705Z. REASON FOR AIR TURNBACK IS INOP CAPTAINS ALTIMETER. INSTALLED BORROWED PART IN SERVICEABLE CONDITION IN CAPTAINS ALTIMETER AS PER M/M 34-13-01. OPS CHECKED GOOD. UPS PART OFF (P/N 4039892-904) (S/N 96073867) BORROWED (P/N 4039892-904) (S/N 043582).