Just a small update,
Mazda USA, Mazda France and Mazda Italy (and Canada) replied but, unfortunately, they couldn't give me any relevant information (well, any information at all, except that it's not a European chassis number, ahah ^^)
anyway, I'll keep on trying to gather any other informations and be posting here what I find :)

Alright,
I've figured out some other things that confirm the US origin of the car :
I need to press the clutch pedal down in order to start the engine. (European models don't require that, and I don't know for the Canadians)
I've got the overheat button/light in the center console.
that one : https://cimg4.ibsrv.net/gimg/www.rx7...51f66a1648.jpg

That being said, I've got also the security button/light too, but I also have the "check engine lights " on my cluster as well. I don't know if the US cars have them or not. Anyway, my cluster had been probably changed since the speedo is in KM/h only.



also, I noticed the car has some small speaker (tweeter?) on the windows panels (both sides), and I doubt this is something all FDs have, isn'it ?
I've no idea if those came with the Bose pack, or whatsoever... I don't have any other bose equipment in the trunk anyway, plus mine should be a R1.
those one : https://cimg7.ibsrv.net/gimg/www.rx7...cbdbc4bce5.png


Otherwise, I didn't advance in my History tracking...
I've been able to talk with the garage in Jacksonville who sold this FD in 92, but they couldn't provide any informations about the vehicle.
I tried to reach the (now closed) society which imported the car to Europe, without success...
And trying to find the previous owner in Italy, but no success at all...

And I'm still refrain from trying carfax, too expensive for only 4 informations that I probably already know...
https://cimg2.ibsrv.net/gimg/www.rx7...61ee81f9ac.png


Seems like I'm currently at a dead end.

Those are just aftermarket tweeters.

Vince

Aftermarket tweeters... alright !

No progress about my FD's history, but working in my garage today I noticed that 99 sticker in the windshield
if it's genuine, it may help me track the history of the car, if only I can figure out where it comes from.
https://cimg6.ibsrv.net/gimg/www.rx7...27dbfe3b9a.png

Ok, small sticker, big improvement.
I've been able to find out where this sticker come from, thanks to a collector's database. ( Switzerland 1999 - Motorway and Parking vignettes )
So, it's a Swiss Motorway Vignette, from 1999 (obviously ^^). This has to be stickied on the windshield in order to use their Motorway, even for foreigners.
If it's genuine, and I guess it must be since it costed 40 Swiss Francs at the time, it's a huge improvement in the car's History. Because it means the car was in Europe for such a long time. Probably in North Italy from 99. (North Italy is pretty close to Switzerland so people used to travel through Switzerland have this sticker)