From MetroAmp Wiki
Drake part # 1204-43 power transformer. Found in Marshall "45/100" 100 watt amps circa 1965 - 1966. This beast with a 3" stack often produced 560-600V DC to the KT66 output tubes.
Color code for Metroamp replica of Drake 1204-43. We adjusted the high voltage secondary to deliver approx 500V, which makes this PT compatible with modern KT66 tubes.
See also, our voltage chart for this transformer: