I had a 50:50 chance to be right:
1- I found a pic somewhere with the '10A' name long ago (ok, it's not a proof).
2- A reliable source (a french magazine) has got the same pic and the additional info I wrote, and also: "En effet, il s'agit d'un vaste véhicule proposé en deux types: 6 A Séries sur un empattement de 310cm et 10 A Luxe de 350cm, dont les prix sont très éléves (jusq'à 55000 F pour le chassis nu 10 A)".
I just thought that the only pic available had to show their top vehicle...