The Chronoswiss Caliber C.674 is a masterclass in horological adaptation, transforming a legendary pocket watch powerhouse into a unique, slow-beating wrist instrument. Found within highly collectible variants like the Chronoswiss Timemaster 24H Day/Night, this manual-wind movement represents founder Gerd-Rüdiger Lang’s obsession with mechanical purity and uncompromising German-Swiss engineering. The foundation of the C.674 is the legendary, ultra-reliable ETA/Unitas 6497-1 pocket watch caliber. Originally designed for mid-century pocket watches, this oversized architecture gives the movement immense durability, huge bridges, and an addictive, highly tactile winding experience. However, Chronoswiss did not just drop an off-the-shelf ébauche into a case; they fundamentally re-engineered its DNA. In its standard form, a Unitas 6497-1 displays time on a 12-hour cycle with a small seconds hand located at the 9 o’clock position. To create the striking 24H Day/Night timepieces, Chronoswiss heavily modified the gear train: * They rerouted the power train to drive a central sweeping seconds hand rather than an offset sub-dial. * The gear ratios were altered so that the central hour hand rotates exactly once every 24 hours, charting the sun’s complete daily path across the dial. * These structural gear train additions required a custom wheel and pinion, adding roughly 0.9 mm of thickness to the movement and requiring an extra jewel (bringing the total to 18). True to the brand’s legacy of transparency, the C.674 is entirely visible through a sapphire crystal exhibition case back. * It features a traditional swan-neck precision regulator mechanism for fine adjustment. * The large bridges are finished with deep, pristine Côtes de Genève (Geneva stripes) and premium perlage. * It utilizes a Glucydur balance with screws paired with a Nivarox flat hairspring and an Incabloc shock absorber. * Polished screw balances and vivid heat-blued screws provide striking contrast across the rhodium-plated surfaces.