2006 marked the first ever in-house automatic chronograph movement for Patek Philippe. The in-house caliber CH 28-520 IRM QA 24H automatic movement features Gyromax balance wheel and a Spiromax hairspring. Operating at a frequency of 28,800 bph (4 Hz), vertical clutch column wheel chronograph, 21k gold rotor, platinum PT950 case in 40.5mm