Websites like TractorData.com offer listings of John Deere tractor serial numbers that provide the model name and the year the tractor was built. This lets tractor owners date their equipment.
It is also possible to derive information from the serial number itself. Current John Deere tractor serial numbers start with "CD." The following four numbers refer to the model of the tractor, the middle letter indicates the emissions level and the final six numbers indicate the numbering sequence for the individual tractor.
Serial number formats change over time. Antique tractor serial numbers, for example, feature a different sequence than modern tractor numbers.