Hamilton serial numbers can be particularly informative, especially for vintage models produced during the brand's American manufacturing era (roughly 1892 through the 1960s). During this period, Hamilton used sequential serial numbers on their movements that have been extensively documented by collectors and historians. Detailed serial number tables are available that can often date a Hamilton movement to a specific year of production with reasonable accuracy.
The serial number on vintage Hamilton watches is typically found on the movement itself rather than the case back, which means the case back must be opened to access it. The case may carry separate markings from the case manufacturer, which for many vintage Hamilton watches was a separate company. It is important to note that vintage Hamilton movements were sometimes recased, so the movement serial number may not always correspond to the original case.
Modern Hamilton watches, produced under the Swatch Group, use different reference number systems. The case back typically displays a reference number that identifies the model, along with the caliber designation for the movement (commonly an ETA or Sellita caliber). These reference numbers can be looked up on Hamilton's website or through authorized dealers. The serial number conventions for modern Hamilton watches differ from the vintage era, and production dating is typically accomplished through the reference number rather than the serial.