They are all very rare today and few have survived.
The first amplifiers made in-house by Fender is the Woodie series, built in 1946 through 1948.
The first of these amps were the K&F models, which were produced between 19.2006 amps have a small metal “Fender 60th Anniversary” button on the back plate. Early Tweeds The early green board tweed-covered amps were not lacquered. It has the same cream board inside with the same components as every other current-production Blues Junior.The serial numbers for these amps begin with “LO,” indicating that they were made in the Fender/Sunn Lake Oswego factory. It usually applies to old vacuum tubes/valves that have gone unsold for decades. All cream board tweed Blues Juniors have a “Limited Edition” plaque on the back.While there have been periods of dramatic change—such as the transition periods between the Leo Fender years and the CBS years or the transition between the CBS years and the current ownership—most models are generally feature-specific and do not change from year to year.Serial numbers are also helpful in determining an instrument’s production year.The finishes were baked in the Kauffman family oven.