Vintage gretsch acoustic dating
As of July 2011, the current thinking is that the first digit probably denotes the year, while the following numbers remain a mystery.
This only pertains the pre-Fender Korean-made guitars.
Unfortunately, correct information can be very difficult to come by.
Most online guides (and quite a few print guides) are based on Jay Scott's groundbreaking book "Gretsch: the guitars of the Fred Gretsch Company," which is a fine book, but is nearly two decades old.
For example, serial number JT03074463 would break down as: Of those, JT is by far the most common on the pro-line instruments.
Each of them can be used to accurately pinpoint the age of a guitar, if you have the correct information.
For example, 27136 should be February (2), 1967 (7) and the 136th instrument made that month. (i.e., 1974 would be 4) Last 3 digits = number of the instrument.