As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TWIN OTTER, RT REAR DOOR WINDOW FELL OUT IN FLIGHT. PN C3FS515-2. BOTH THE WINDOW AND SEAL WERE MISSING WHEN PLANE LANDED. THE SEAL WAS PN C3FS515-3 AND FILLER PN C3FS515-4. MFG NOW SELLS A NEW AND IMPROVED SEAL PN C3FS 515-5. IT IS RECOMMENDED THIS WINDOW IS CHECKED CAREFULLY AT EVERY PREFLIGHT. (K)