Three Mk1 chassis were produced with the original aluminium construction, but the fourth incorporated advanced and exotic metal alloys. This included extensive use of titanium for many of the componentry, and a high percentage of magnesium sheet in the monocoque panelwork. Owing to its novel construction materials this car, chassis number 104, was referred to as the "Ti-Mag Car". Gurney was well aware of the risks involved in driving a car made from such flammable materials. After witnessing Jo Schlesser's death in a magnesium-fuelled fireball during the 1968 French Grand Prix, Gurney compared racing in 104 to ""driving a Ronson cigarette lighter"".