Dating of fender amplifiers
Amps from the silverface era, which have a silver faceplate, were manufactured from 1968 to 1982.
In 1992, Fender began producing the '65 Reissue Twin Reverb. According to Fender, amplifiers produced through 1969 have a sticker near the tubes.
On early amps, this material was varnished to make it a more durable covering.
Several different types, in vertical and diagonal weaves, were used.
DATING CONTEMPORARY FENDER AMPLIFIERSAll Fender amplifiers manufactured from 1990 to the present include a date code, printed on the quality assurance (QA) sticker on the back of the amp chassis.
This black-and-silver sticker contains several lines for “sign-offs” on completion of sound and electrical testing.
Fender recommends dating unstamped amps by the EIA number on the transformers.
The format is always EIA 606-Y-XX or 606-YY-XX where Y indicates the year (196Y/197Y or 19YY respectively) and XX the week. Dating by serial number, while less accurate, can be of some use.
They are not of a concern with dating as only the 2 letter date codes on whichever chart or sticker and the transformer number comes into play for that....
If three digits are present, the first digit refers to the year (i.e., a “7” would mean 1967).
If four digits are present, the first two digits refer to the year (i.e., a “66” would mean 1966).
The last two digits refer to the week of the year (i.e., a “26” would mean the 26th week or, roughly, June).
For example, EIA 606-4-21 would denote the 21st week of 1964.