A reference number in watchmaking is a unique identifier assigned by manufacturers to each model or variation of a timepiece. These alphanumeric codes provide essential information about the watch's specifications, including the model type, materials used, features, and version or revision. The model type indicates the overarching design or collection the watch belongs to, while materials detail the case, strap, or bezel components. Features may include complications like chronographs, moon phases, or water resistance. The version or revision highlights differences in color, dial design, or production batches. Reference numbers are crucial for verifying authenticity, offering insights for collectors, and assisting in maintenance by helping service centers source the correct repair parts. Each brand has its unique system for assigning these numbers, which often follow a logical structure, such as initial digits indicating the model or collection, a middle segment specifying material type or dial color, and final numbers highlighting complications or production details.