Gibson stamps serial numbers on all its guitars on the back of the instrument's headstock. The number is printed perpendicular to the instrument's neck on guitars with "book" headstocks such as the SG and Les Paul. The serial number runs parallel to the neck on the Explorer and Firebird.
In Gibson's modern serial number scheme, the serial number's first five digits correspond to the instrument's date of manufacture. The sixth digit is the batch number of the guitar, and the seventh is the instrument's rolling production number. Unfortunately, Gibson has only used this system since 1977, and the company used many different numbering schemes prior to this date. Dating a guitar built before 1977 usually requires contacting Gibson for assistance.