Well, that's a very fine bit of sleuthing from SLB, I'd never heard of either Donnet Leveque or FBA before I encountred this beauty. I wouldn't have a scooby about their differences, sorry! I just saw this thing in a museum and thought, "hey, there's a rare one for the challenge". I might have known it wouldn't last long against some of the intellects here!
I imagine it is now merely a formality but I shall leave it to you (unless someone else beats you to it) to make the definitive judgment.
I say again, "it is not a Portuguese design".
There is a coach museum nearby.
That should do it!