Received pictures of your data plates and I concur with your interpretation of the bulk of the data.
The production code 28C820392P breaks down as:
28C= Scheduled for production on March 28,'57
82= FMC Export Operations, New Jersey
0392P= 392nd item scheduled for
production (Interpretation
may vary) Some say its for the DSO, others say total
production that day.) Seems obvious in this case. The "P" means "scheduled" or "Planned" and may not have occured.
Your identification of color and code is correct except the soft top color never appeared on the data plate. Also, your car apparently was delivered with the soft top only. Your invoice will confirm/refute this. You also asked why 40A appeared sometime as the model #. During the '55 and possibly the '56 model run, the model 40 indicated a Thunderbird and the A or B suffix indicated hard or soft top. I don't think this was carried into the '57 model run.
The French Data Plate is the first I've ever heard about. Very interesting! All I can do is venture some guesses on the translation. My guesses closely coincide with yours. D 7 S may mean a D engine (312, 245 H P) 7 is the model year and S is the designation for Thunderbird in the FoMoCo part numbering system. The indicated weight of 1780 Kg. seems way out of line. That is just under 2 tons! I registered a new '57 in Michigan where the license fee was determined by weight. It weighed just under 3200# for registration purposes and the license cost $10.85. Are you listening Governor Ahnold?
Different governmental jurisdictions had differing methods of taxing vehicles. Some states used value, others used weight, and a few may have had H.P. or engine size as a taxing standard. Other countries including those in Europe and Asia were death on engine size and output. Even some Canadian Provinces used taxable H.P. as a standard back then.
Consider posting those pixs of the data plates on your web site. We may pick up some expert input or at least some interesting theories.
Tom D.
