What was found
PILOT ALTIMETER ALTITUDE SELECTOR KNOB BROKEN, CAN'T SELECT ALTITUDE, BARO, IN COLLSMAN WINDOW. RETURNED TO DEPARTURE AIRPORT. REPLACED ALTIMETER.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
PILOT ALTIMETER ALTITUDE SELECTOR KNOB BROKEN, CAN'T SELECT ALTITUDE, BARO, IN COLLSMAN WINDOW. RETURNED TO DEPARTURE AIRPORT. REPLACED ALTIMETER.