The Brownface series was introduced in 1959 and discontinued in 1963.This period marked the beginning of Fender's use of Tolex to cover amp cabinets.
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.
Fender later on constructed them with "narrow panel", in which all the panels have more or less the same width.
Toward the end, despite keeping such construction, Fender utilized tolex to cover its amps.
The name 'brownface' stems from the brown-colored control panels, common to both the brown- and cream/blonde- Tolex-covered amps.
The brownface amps originally featured a dark maroon or "oxblood" grillcloth, which was changed to "wheat" in 1962-63.
Fender began using silicon rectifiers to reduce heat and voltage sag caused by tube rectifiers, and introduced an all-new, very complex vibrato circuit.
The shift from the tweed design to tolex occurred in limited production in 1960.
Namely, the introduction of the stand-alone spring reverb unit in 1961, followed by the subsequent incorporation of the reverb circuit within a combo-amp design with the 1963 Vibroverb.