Dating fender tweed amplifiers
The Dual Professional was the first to have tweed covering, a top-mounted control panel and a tube chart, which would eventually become standard for all but the smallest amp models.
1980/1981-1982 New Blackface: A black control panel was re-introduced again with slight changes from the 1960s Blackface models.
If you are unable to determine the approximate production year of your amplifier using the above charts, there are other means of dating Fender amps.
Several excellent books are available that contain reliable and invaluable information on the history of Fender amplifiers.
When trying to determine the date of an Fender amplifier, it is useful to know a few things about feature changes that have occurred over the years.
Serialization on Fender amps is not a reliable way to date them as records of these were not kept until 1994; however, Greg Gagliano has compiled several hundred serial numbers on Fender amplifiers and has put together an extensive list.