The Fender Twin Reverb Master Volume model was based on the Twin Reverb, launched in 1963, itself based on the Twin Amp that started its evolution as the 15-watt 1952 Twin. The Twin Reverb and Twin Reverb Master Volume versions pushed about 85 watts through a pair of 12-inch speakers, but in 1981 that power level rose to a peak of 135 watts. https://reverb.com/p/fender-twin-reverb-2-channel-135-watt-2x12-guitar-combo-1977-1981