Dating fender amps by serial number part vi
The guide for that is much simpler: be nice, ask questions, offer beer.
If you have absolutely no idea whether your Marshall is old or new, a good place to start is the model name or series.
This era saw the advent of Plexiglas panels (giving rise to the "Plexi" name) and four-digit model numbers.
The first Marshall amps were made in England starting in 1962.
Production has continued there uninterrupted through today, though some lower-priced models are now made in China, India or Korea, depending on the series.
Halfway through 1963, the switch was made to the CTS brand (137). In that year the Jensen production was transferred to Rola. When Rola started making speakers for Jensen in 1972, Rola also used Jensen's EIA code in the beginning (220). Please note, old Fender amplifiers may look old, but are not.
For example, speakers, potentiometers or transformers may have been replaced,or the coating of the amplifier/cabinet is renewed (re-tolex).