Gibson Serial Number
Same format, but first digit and fifth digit both same number. Example: 91234567 = 2009? No — 91234567: digit1=9, digit5=6? Mismatch. So invalid.
82765501
Same format, but first digit and fifth digit both same number. Example: 91234567 = 2009? No — 91234567: digit1=9, digit5=6? Mismatch. So invalid.
82765501