Fender Tube amp codes:
1953-1970 - (look for a 2 letter code stamped on the tube chart inside the back of the amp)- the first letter is the year, and the second letter is the month. An amp stamped NA would have been made in Jan. of 1964. Here is a list of the first letter showing the year of manufacture.
    A=1951, B=1952, C=1953, D=1954, E=1955, F=1956, G=1957, H=1958, I=1959, J=1960,
                            K=1961, L=1962, M=1963, N=1964, O=1965, P=1966, Q=1967
A=Jan, B=Feb, C=Mar, D=Apr, E=May, F=Jun, G=Jul, H=Aug, I=Sep, J=Oct, K=Nov, & L=Dec
•         Fender Electric Blackface amps from 1964 to early 1965
•         did not have a Fender Logo on the grillcloth.
•         Silverface amps with aluminum trim surrounding the grill cloth are 1968 models
•         A push-pull pot was added to some amps in 1974.
•         Therefore, if you have a push-pull pot, your amp is 1974 or newer.
1970-1989 -Most amps do not have a date code stamped on the tube location chart. These codes are for amps with the serial number beginning with a letter:
B+5---digits - 1975-1976
A6+5-digits - 1976
A7+5-digits - 1977
A8+5-digits - 1978
A9+5-digits - 1979
F0+5--digits - 1980
F1+5--digits - 1981
F2+5-digits - 1982/83
F3+5-digits - 1983/84
F4+5-digits - 1984/85
F9+5-digits - 1979-1980
EIA numbers taken from the transformers may help you to determine the date of production on amps that fall between the different dating schemes. These numbers always begin with "606", and are followed by three or four digits in various combinations. If three digits are present, the first digit would refer to the year i.e. ("7" would mean 1967). If four digits are present, the first two digits refer to the year i.e. ("66" would mean 1966). The last two digits would refer to the week of the year i.e. ("26" would mean the 26th week or approximately June). An example would be: EIA 606-4-21 would mean the 21st week of 1964.
All Fender amplifiers, manufactured after 1989 include a date code on the amplifier.
This code is located on the "QA" (Quality Assurance) sticker, which may be found on the back of the amp chassis. The sticker is a Black and Silver label, which contains several lines for "sign-offs" at the completion of sound and electrical tests, where applicable. The last line will have 2 letters of the alphabet either printed or written by hand. These letters are the production date code for the amplifier. The first letter refers to the year, and the second letter refers to the month of manufacture. The codes are:
1990-A  1991-B  1992-C  1993-D  1994-E  1995-F  1996-G  1997-H  1998-I 
1999-J    2000-K   2001-L   2002-M   2003-N  2004-O 2005-P 2006-
REFERENCE MATERIALS FOR DATING FENDER AMPLIFIERS
A few books are available for dating Fender amps, which have  information on the history of Fender amplifiers. You will need to get the date codes from the speaker frames, the potentiometer date codes, the transformer codes and as much other detailed information you can about the specs and features of your amp. If you have a serious interest in learning about the history of Fender amplifiers, or if you just want to try to establish the year of production of your own amp, I recommend that you pick up the following book.
"Fender Amps the First 50 Years", Teagle & Sprung, 
                                   FENDER AMP SPEAKER CODES
This chart will identify the speaker brand used in your amp.
Fender used speakers manufactured by the following companies:
•             Altec-Lansing -#391
•             CTS - #137
•             Electro-Voice -#649
•             Eminence -#67
•             Jensen - #220
•             Oxford - #465
•             Rola -#285
•             Utah -#328
Jensen supplied all Fender speakers until approximately 1961.
Since 1962 Fender used speakers from all the above companies