Thanks for the point! The photographs that I used for reference are here (I'll send the links by PM upon request). The captions on the photographs read:
#1: Count Jules-Albert de Dion (right) with his stoker.
#2: Graf Albert de Dion und Georges Bouton, ca. 1895
#3: Rare photo taken during the actual 1894 Paris-to-Rouen race. Comte Jules-Albert de Dion (front, right) is driving with his stoker seated to his left. Georges Bouton sits with his back to de Dion, and Bouton's brother-in-law Charles Trépardoux is to his right with his back to the stoker. The other two passengers were Captain Émile Driant and the Baron de Zuylen de Nyevelt. The name of the stoker is unknown to me at this writing.