This Patek Philippe Annual Calendar reference 5146P-001 is one of the Maison's most enduring modern complicated references. Its self-winding caliber 324 S IRM QA LU combines an annual calendar with moonphase, while the power reserve indication adds another layer to a display already closely identified with the model. For a collector drawn to Patek Philippe's early 21st century complicated watches, this is the reference that kept the annual calendar in a classical key even as the firm's broader output moved in other directions. In platinum, the case measures 39mm across and 11.5mm thick, a size that gives the watch enough substance without disturbing its formal balance. The gray dial is the defining note of this configuration, lending the reference a cooler and more restrained character than its warmer precious metal counterparts. Few modern Patek complications balance utility and proportion with quite this much ease, which is why the 5146 remains such a persuasive expression of the annual calendar at Patek Philippe.