Sorry, it's not a Weiss Manfred -- which, according to the info I have, would be known by the full name & not the initials.
A couple of hints:
(1) One make has been guessed that's in the puzzle, but it was guessed it for the wrong car. *Edit* - Disregard this hint; it was made in error.
(2) Every remaining unguessed car was made in one of two countries.