The tube chart date code works like this: the first letter indicates the year and the second letter indicates the month.So if your blackface amp has a date code stamp of OB, it was made in 1965/February.: The transformer number tells you when the transformer was made and not necessarily the date the amplifier left the Fender Factory, the “2 Letter” date code on the Tube Chart or QA Sticker actually tells you that and that makes it the most accurate option for dating the month and year it was made....The type of face, grille cloth, type and number of speakers, type and number of knobs, etc.
We combined all of our information into a computerized database for this project and for the past 18 months have been slowly (sadly, very slowly) gathering information that we collect ourselves as well as from other people. What we need is the following: 1) Model name 2) Model number on the tube chart 3) Date code letters on the tube chart 4) Speaker codes (if speaker is original) 5) Transformer codes (if the amp doesn't have date codes on the tube chart) 6) Cosmetic features (flat/raised logo, tweed/tolex, blackface/silverface, rough/ smooth blond tolex, white/skirted knobs, TV-front/wide-panel, etc.) One very interesting and very important factoid has surfaced regarding the date code letters on the tube chart.Devin runs Doc's Music in Springfield, Missouri and his interest lies in the woodie and tweed Fender amps made from 1946 through 1960.Greg and Devin's experience meshed well with mine since I'm essentially the blackface/silverface amp guy (amps made between 19) in the group.Now if it’s a blackface amp, it’s a safe bet that 6 means 1966. This code can be found on the power transformer, output transformer, choke, and reverb transformer.They are all usually within a few months of each other.Greg is a long time Fender collector who is very knowledgeable not only in the details, but in the circuitry as well.His particular area of expertise is in Fender amps made from about 1960 through 1967.Most post tweed Fenders had trannys manufactured by Schumacher.They used a code like this: 606 – 645 The date is in the last three digits, after the 606 – .After reading Teagle and Sprung's excellent Fender amp book, I took them up on their challenge that maybe someday someone will compile enough serial numbers so that Fender amps can be dated that way. I contacted several Fenders collectors and dealers who were kind enough to supply me with data.I turned to the Internet to do some more networking which resulted in a major turn of events as I met two individuals who have become instrumental partners in this project: Greg Huntington and Devin Riebe.