I think this is still accurate...

- serialnumber.jpg (52.78 KiB) Viewed 15207 times
The pattern is as follows:
YDDDYRRR
YY is the production year
DDD is the day of the year
RRR is the factory ranking/plant designation number.
Prior to 1984 when the Kalamazoo, MI factory was closed, the numbers 001-499 indicated Kalamazoo production. Ranking numbers 500-999 continued to indicate Nashville production through 1989.
Since 1989, all Gibson acoustics are built in Bozeman, MT and all Gibson electrics are built in Nashville or Memphis. Ranking numbers for Bozeman start each day at 001 and the electrics may start as low as the 300s.
Examples: 70108276 means the instrument was produced on Jan. 10, 1978, in Kalamazoo and was the 276th instrument stamped that day.
82765501 means the instrument was produced on Oct. 3, 1985, in Nashville and was the 1st instrument stamped that day.