So if you find pots from late 68 and transformers from early 69 you can be pretty sure your amp is a 1969.Serial Number: There is no information readily available for dating Fender amps by serial number but there are people working on it. Circuit Code: In 1963 Fender stoped using model numbers to identify schematics and began using the model name and an assigned circuit number.
In 1992, Fender began producing the '65 Reissue Twin Reverb. According to Fender, amplifiers produced through 1969 have a sticker near the tubes.
This is commonly stamped with a two-letter date code.
The first letter indicates the year: M 1963 N 1964 O 1965 P 1966 Q 1967 R 1968 S 1989 The Second Letter indicates the month: A January B February C March D April E May F June G July H August I October J September K November L December Check the EIA number.
This is included in the "blackfacing" conversion or can be done to many other amps as a separate mod.
• Convert circuit to Blackface specification (see below).