Remember, your amp is newer than the newest component.
For example, if you find pots from late ‘64 and transformers from early ’65, you can be pretty sure your amp is a 1965.
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.
These circuit numbers which are located on the tube chart can be usefull for getting a rough date on an amp.
If your amp dosen’t have a date code, flip the amp upside-down and check the transformers, and speakers for their manufacturer codes.So if you find pots from late 68 and transformers from early 69 you can be pretty sure your amp is a 1969.