So if you find pots from late 68 and transformers from early 69 you can be pretty sure your amp is a 1969.Serial Number: There is no information readily available for dating Fender amps by serial number but there are people working on it. Circuit Code: In 1963 Fender stoped using model numbers to identify schematics and began using the model name and an assigned circuit number.Stamped on the metal backing of most amps is the serial and production number. The following list, compiled by Greg Gagliano, establishes dates through 1976: A00100 to A01200 - 1964 A01200 to A04300 - 1965 A04300 to A07000 - 1966 A07000 to A10400 - 1967 A10500 to A11300 - 1967 A10500 to A16500 - 1968 A16500 to A21400 - 1969 A21400 to A25600 - 1970 A25600 to A37000 - 1971 A37000 to A50500 - 1972 A50500 to A68000 - 1973 A68000 to A99999 - 1974 A81000 to A99999 - 1975 B01000 to B15000 - 1975 B15000 to B68000 - 1976 If these steps are unsuccessful, a number of books have been published that help to date amps based on part codes. • Convert to a better bias adjustment circuit for improved tone and longer power tube life for your silverface Fender amp?Fender recommends dating unstamped amps by the EIA number on the transformers.
In 1992, Fender began producing the '65 Reissue Twin Reverb. According to Fender, amplifiers produced through 1969 have a sticker near the tubes.First use the cosmetic features to get a range of possible years.Next, (if applicable) look for the date code on the tube chart.The code is simple, the first two letters are the revision, where AA is the first revision, AB is the second, etc.The next one or two numbers are the month where January is 1 and December is 12. Example: AB763 = second revision, July, 1963 AA1070 = First revision, October, 1970 Misc Dating Info: Silver face amps with the aluminum trimmed grilles are from 67 or 69.