If it’s a one digit year you need to determine the correct decade of the amp some other way.
ZZ = a number from 1 – 52 indicating the week of the year.
There are exceptions to this rule like the the Bronco.
Instead, there were approximately 2000 of these chasses produced, which then ended up as one of the three models in question.
It would be more accurate to say that approx 650 of each of these models were produced in ’60.
Fender’s amps, unlike their guitars, are not tracked by the serial number.
In order to date a Fender amp or provide the value, you need to know one of the below: * The 2 letter date code rubber stamped on the Tube Chart, or * The 2 letter date code on the QA Sticker, or * The Transformer Number that starts with “606-XX-XX”, with the 3 or 4 Xs being the unknown numbers that need to be provided by the owner of the amplifier asking the question.