This Patek Philippe Annual Calendar reference 5035P-024 is the watch that introduced the complication to the modern market. Its self-winding movement carries the annual calendar alone, the mechanism Patek launched here as a more usable calendar for regular wear and one that became a permanent part of the firm's output. That position gives the reference a place beyond its size, since the 5035 is where the entire line begins. In platinum, the case measures 37mm across and 10.5mm thick, a proportion that keeps the watch squarely in the classical vein. The silver dial matches the restraint of the layout, with the calendar display spread cleanly across the upper half. For a collector drawn to first-series complications, that origin is the reason to own it. Few modern Patek references have introduced an entirely new complication with such lasting consequences for what followed.