As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LOSS OF POWER ON TAKEOFF, RETURNED TO AIRPORT. AFTER LANDING HE AGAIN CHECKED HIS MAG DROP AND REPORTED HIS LT MAG DROP TO BE ABOUT 300 RPM. FURTHER INVESTIGATION FOUND THE ONE OF THE IMPULSE COUPLING PAWLS ON THE LT MAG HAD BROKE IN HALF AT THE PIVOT POINT. THE PIECES FELL HARMLESSLY INTO THE OIL SUMP AND WERE REMOVED. (K)