Likewise, the brown/blonde Tremolux, Concert, Vibrasonic, Twin, Pro, Super, Vibrolux, Showman, Dual Showman, and Bandmaster used a sequential numbering independent of model, but as with Fender guitars, these were not used consecutively. The 1956 to 1963 Champ, Harvard, Princeton, Deluxe; the 1956 to 1960 Vibrolux, the 1956 to 1964 Bassman, and all the tube reverb units have their own serialization scheme.
These say "Fender Electric Instruments." Depending on the model the use of these pre-CBS panels have been observed on amps as late as August 1965, except for Champs and Vibro Champs which had foil stickers on the back the chassis.
Fender must have had a million of these labels printed up since they appear on Champs and Vibro Champs well into 1966.
If anyone has an amp with a "PA" stamp, please let us know.
Still, I wouldn't be too quick to just glance at that tube chart and accept an "OA" as a January 1965 amp.
New panels made after the CBS acquisition were used beginning in April 1965 and say "Fender Musical Instruments." So, if you have January 1965 amp, it will have a Fender Electric Instruments panel whereas a January 1966 amp (even though it has that green "OA" date stamp) will have Fender Musical Instruments. Although the database doesn't have thousands upon thousands of entries, we are seeing some interesting patterns emerging that will help date amps by serial number. The early amps (woodie and tweed) had serial numbers handwritten on the tube chart.
These appear to be used sequentially independent of model.
The factory realized its mistake in February because these amps have a "PB" date code in black ink.
Now, we obviously haven't looked at every amp made in January 1966 so this isn't set in stone.
This makes things a little more interesting and difficult in playing the "dating game." And yet there is another variable to contend with as it appears that models that share chassis may also share the same serialization scheme.