These serial numbers are preceded by 2 digits. 99 = 1975, 00 = 1976 and 06 = 1977. Gibsons most sustainable numbering system was launched in 1977, an eight-digit number. The first and fifth digits represented the year of manufacture.

How do you tell the year of a Gibson guitar?

There should be a space after the 1st digit with the 4 and 5 digit serial numbers, and no space with the 6 digit numbers. The 1st digit indicates the year of manufacture for the 4 & 5 digit serial numbers, these were used from 1989-1999.