Guitar amplifier dating by serial numbers - How To Date A Guitar Amp or Bass Amp By Serial Number.
There are a number of resources available online to help you to date your guitar amplifier or bass amp.
A 1957 tweed Vibrolux was reported with a tube chart printed with circuit “5E3” (tweed Deluxe) instead of the correct 5F11 (see photo).
Clearly Fender wasn’t afraid to use incorrect parts when they were in a bind. The 5G12 Concert is the earliest version from very late 1959 and early 1960 so the existence of a tweed example, while extremely rare, is certainly plausible since Fender was making lots of tweed amps during the same time period.
Dating an amplifier by serial numbers can be effective as well.