My 2nd F3 purchase needed a few parts freed up and it is working great now. But during the maintenance a small brass spacer tube fell out of the camera. Not an uncommon occurrence with camera repair but this time I cannot find where it goes back in. Nothing like this fell out of my other F3. I have looked at the schematics of the areas I worked on but no part like this seems to show on the drawing. I only removed the base plate, shutter winder arm and button, camera back and view finder. I suspect the part dropped out of the base area but I cannot see anywhere it will go back in. Camera is working fine. Image of part attached. Thanks for your interest.
