DATING FENDER AMPS BY REFERENCE OF SERIAL/CHASSIS NUMBERS
Dating older Fender amplifiers from before 1994 is difficult because no proper records were kept.
An exact date is therefore not to define but is an approximation.
On the inside of the cabinets of Fender amplifiers that were built after 1950 and before 1970, a sticker is generally attached. This indicates the type of the tubes used and their location on the chassis. Also on this sticker stamped two letters (sometimes handwritten) indicating a date code.
All Fender amplifiers manufactured from 1990 until now, have a date code printed on the quality assurance (QA) sticker on the rear of the chassis. This black-silver sticker shows signatures or initials of employees after the finished noise and electrical tests.
The last line also has a stamped or handwritten two-letter date code. Handwritten is sometimes difficult to read (see image).
The first letter is the year and the second letter is month.
If no QA or tube location sticker is found or it is bad read, look at the rear of the chassis on the right side where a chassis number is punched. You can decipher the year of construction using the date decoder.
Some indications that you can also recognize the production year.
Before the CBS era (before 1965) Blackface amplifiers were feature labeled Fender Electric Instrument.
Blackface amplifiers from 1964 and some from early 1965 did not have the Fender logo on the grill cloth.
After the acquisition of Fender by CBS in January 1965, amplifiers were labeled as Fender Musical Instruments.
From 1974 a potentiometer with pressure-pull switch was added to some amplifiers.
The logo on the grill cloth of the amplifier also gives an indication of when it was produced.
A logo with tail is from before 1973. After 1973 the logo was tailless. With few exceptions. As long as there was a stock with tail logos, they were used randomly in 1973.
Amplifiers from that year and perhaps also in 1974 can therefore have the new or old logo.
tailless (after 1973) with tail (before 1973)
Dating of components
If there are no sticker or chassis number at all, the the components can also offer a solution for dating the year of construction of the amplifier.
(Assuming the components is original and has not been replaced.)
With help of the EIA (Electronics Industry Association) number on the transformer, the production date can be determined.
This is not the production date of the amplifier, because the transformer has already been made before and may have been for a while in storage.
With 3 digits, the first digit is the last digit of the decade of the 20th century. The last two digits is the week of that year.
At 4 digits, the first two digits are the year of the 20th century.
Example: 606 6849 is 1968 week 49. If the production date of the transformer is now known, add at least 6 months to the production date of the amplifier. From the example, the amplifier could have been built in 1969.
Transformer date decoder
Speakers and potentiometers
What applies to the transformer also applies to speakers and potmeters.
Fender used Jensen speakers until 1972.
In that year the Jensen production was transferred to Rola. (Rola was already a part of Jensen). When Rola started making speakers for Jensen in 1972, Rola also used Jensen's EIA code in the beginning (220). At the end of 1972, Rola changed the code to 285.
Sometimes Fender used CTS speakers in the 1960s. Between the mid 1960s and early 1970s, the CTS 10-inch Alnico was regularly used in Super Reverbs.
Eminence (founded in 1966 by former CTS employee Bob Gault) made speakers especially for Fender according to those specifications. From the early eighties these were standard in almost all tube amplifiers.
Despite the fact that the Utah speakers from the 50s and 60s were of very good quality, Fender did not use them much during that period. It was not until the 1970s that these spaekers became more widely used.
But not all speaker manufacturers work with an EIA code.
For example, Celestion has its own date coding method that consists of 2 letters with 1 or 2 digits.
Example: GK12 is July 12, 1977.
23HA is August 23, 1956 or August 23, 1968.
The Celestion dating system is included in the speaker decoder.
Speaker date decoder
In the 1950s, Fender mainly used potmeters from the Stackpole brand (304). Halfway through 1963, the switch was made to the CTS brand (137). In 1967 Fender bought a very large stock of CTS and was used for over 5 years. Amplifiers (and also guitars) made in 1973 can therefore still have the 1967 potmeters with EIA numbers from the stock that was purchased in 1967.
(see also Potentiometer decoder)
More manufacturers can be found with the EIA factory decoder by searching on their EIA code or in the component list.
EIA factory codes