His initials are in the name of other one of its cars
I must confess I did not understand that...but:
Mario Marsonetto: MM, Marsonetto Luciole: ML, Marsonetto Mars: MM.
Looking at the solution now I understand that probably you meant that he used his intitials MJ for his other creation.
Jacques Morin?
Panhard by André Morin (SOVAM)
I thin they are 2 different people...