They are all usually within a few months of each other.
Use the latest one to give you a good idea of when it was made.
For example, if your silverface super reverb has transformer codes all from 1974, it was made in 1974! Based on the last number (45), it’s safe to say it was made in late 1974.
Many silverface and some blackface amps have the exact week, month and year stamped insie the chassis.
I can't tell you or anyone else anything from the serial number, Fender's amps are not tracked like their guitars by the serial number.
In order to date your Fender amp or provide the value I need to know one of the below;* 2 letter date code on the Tube Chart, * 2 letter date code on the QA Sticker, or * The Transformer Number starting with "606-" followed by 3 or 4 additional numbers and insert the dash (-) marks as they separate the month from the year of manufacture.