If I have this we so far have seen presented three or four examples from the same plant and same possible production period and a couple from about the same time and plant. Believe at this point we're all just sharing and "talking". Believe Chris is just following along with what we have practiced since the site opened. Having an open minded and fact based discussion is good for us and the history of these cars.
To further the discussion I would also be interested in how many fastbacks from same plant and period have the original rivets and how many fastbacks from through out the year turn up with screws. This might support that it was make due practice from earlier owners and "restorers" that choose screws over rivets.
Lots of possible rabbit trails that either go some where or don't
Won't know unless we chance them either privately or as a group
This is not to suggest that we have to chase every thread and every possibility but as we've suggested before. One car is just one car. Find three - four - five unrestored examples from same plant and time with the same detail then it might be worth the time to check it out. Just an opinion and long held practice of some of us