Dating Fender Tube Amps by Serial Number, Part I by Greg Gagliano Copyright 1997, 20th Century Guitar Magazine. Well, we'll get to good parts, but first a little background information is in order.

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.

There are several ways of identifying a manufacturer, or particular part number of a component in most audio gear that's been manufactured since the mid 1950s.

There's an EIA (Electronic Industries Association) code that identifies the manufacturer, or company, sometimes stamped (either in ink, or metal embossing, or ID tag) on the particular component - in this case the transformer.

A00100 to A02000 – 1964 A01200 to A08100 – 1965 A08100 to A17000 – 1966 A16000 to A21000 – 1967 A20000 to A26000 – 1968 A25000 to A28000 – 1969 A28000 to A29000 – 1970 A29000 to A32000 – 1971 A32000 to A35000 – 1972 A33000 to A39000 – 1973 A39000 to A42000 – 1974 A42000 to A51000 – 1975 A51000 to A53000 – 1976 Export models had serial numbers that started with a “B” rather than with an “A”.

Transformer / Speaker / Pot Codes American-made electronic components of that era usually have codes to indicate manufacturer and date of production.

If anyone has an amp with a "PA" stamp, please let us know.

Still, I wouldn't be too quick to just glance at that tube chart and accept an "OA" as a January 1965 amp.

For example if you have 606-432 on a transformer, you can tell that it's a Schumacher transformer from the '606', the year is either 1974, or a 1964, from the '4', and the '32' is the week of production.

The model type, or number, is sometimes stamped on the transformer frame, or bell, as well; for example 022798, telling us that this is the power transformer from a Fender Super Reverb.

However it’s unlikely that the transformer found its way immediately into production, so it’s a pretty sure bet that the a 1975.