A ref. 5370P-001, the brand's landmark first entirely in-house, three-button split seconds introduced 2015 with a black grand feu enamel dial. Conceived under Thierry Stern with movement development led by Philip Barat and design overseen by Sandrine Stern, it was built to showcase full in-house chronograph mastery. Its calibre CHR 29-535 PS combined six patented chronograph innovations with a newly engineered rattrapante mechanism that offered smoother engagement and more stable amplitude than earlier generations. Today, the 5370 stands as one of Patek’s most technically important modern complications and a benchmark for the traditional Genevan high complication.