Working through the running change list for 1965 San Jose built fastbacks today so figured I would share and invite others to submit their findings and observations. Think I have it narrowed down pretty well given we don't know when any of the cars were really build but at least we can provide how to determine if the car is apart how they were equipped and some guidance for those that are fully assembled.
Just as a review. A long time ago it became apparent that earlier built fastbacks lacked the coat hooks on both sides of the interior for some reason. Not sure if the designers didn't like the look but sales determined (maybe customer complaints) that they were wanted/needed.
Since the location of the hook was added to a spot in the roof side rail where an opening was already present the fix was an addition of a small plate welded over the hole during unibody assembly as shown below. Like above - Earlier car, upper left - Later car, lower right
May 8th 2021 Update: After collecting and looking at the data assembled it appears that the change from no coat hooks on fastbacks to having them took place approximately between the end or so of April and the middle of May 1965
Highest 65 San Jose vin for a fastback with no coat hooks or attachment found was 5R09x2149xx with a scheduled build date of 4/29
Lowest 65 San Jose vin for a fastback with coat hooks or attachment bracket installed found was 5R09x2174xx with a scheduled build date of 5/12
Of course cars were not built in sequential order so any of these dates must be viewed as approximate dates and VIN when applied to other cars but they should provide a fairly reliable range for comparison