With this new 9907 MC calibre, produced, developed and prototyped exclusively in-house in La Chaux-de-Fonds, Cartier is revisiting the chronograph function through this pioneering version of the Rotonde de Cartier model. The primary distinguishing feature of this new Rotonde de Cartier 9907 MC calibre watch is the isolated chronograph display in the centre of the dial.

This ingenious arrangement offers both exceptional legibility of this traditional complication and a novel way of displaying the time. Timekeeping occurs on two levels: the lower level is devoted to displaying the hours and minutes using blued hands which are invisible save for the tips, while the upper level is dedicated to the chronograph function. In the centre, the slim blued seconds hand begins to move when the corresponding push-piece is pressed, while the large counter in the form of an arc records each of its revolutions up to thirty minutes. Thus, the hands indicating the time never obscure those of the chronograph.

The Cartier Watches watchmakers decided to substitute the usual horizontal release system mounted on a lateral yoke, which requires a large amount of energy, for a vertical alternative with an extremely modern design.