These serial numbers are primarily associated with two distinct, non-overlapping periods in Gibson’s history: (the most famous era for 6-digit numbers) and 1975–1977 (a transitional period). Knowing the format and features is key to correctly identifying your instrument. Part 1: The Golden Era – 1961 to 1969 From 1961 through 1969, Gibson used a 6-digit serial number stamped into the back of the headstock. This is the system found on iconic models like the SG, ES-335, Firebird, and later '60s Les Pauls (reintroduced in 1968). How to Decode a 1961–1969 Serial Number The first digit indicates the last digit of the year , but the pattern changes in 1966.