This is the Franck Muller 5850 CC Pulsation Scale Chronograph. Renowned watchmaker Franck Muller began restoring watches for brands like Patek Philippe before founding his own brand in 1991. Known as the "Master of Complications," he crafted intricate wristwatches, earning recognition for some of the world's most complex designs.

Although Franck Muller's brand isn't as prominent as in the early 2000s, his early work has recently gained attention with the neo-vintage revival. The 5850 Double Face Lemania Chronograph is a notable example from this period, standing out among other Lemania-based chronographs.

The rare 5850 CC DF combines Franck Muller's Cintrée Curvex case with a double-face complication. This unique design features a secondary face on the back with a telemeter and tachymeter scale, while the front displays the chronograph. It is less common than its round counterpart, blending the watchmaker's finest elements.