As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE PERFORMING AD 96-12-07, THE MECHANIC NOTICED THAT THE STOP PIN FOR THE IMPULSE COUPLING WAS MISSING. INSPECTED THE ACCESSORY SECTION AND FOUND THE PIN WEDGED BETWEEN THE CRANK CASE AND A GEAR. REMOVED THE PIN, NO FURTHER DAMAGE WAS FOUND.