Yamaha instruments have serial numbers so that collectors and players can ascertain the manufacture date, the authenticity and other related information about the instrument. Yamaha keeps a database of serial numbers to validate the authenticity of instruments.
Without serial numbers, it would be difficult to distinguish Yamaha makes and models of different years from one another. Certain instrument serial numbers are highly valued as vintage collectibles, and Yamaha must maintain a way to tell these instruments apart from more ordinary models. Many user-submitted serial number databases are available on the Internet that chart the manufacture year for older instrument models.