There were a number of variations on these designes offered over the years. There were at least three different sets of tubes used. The first were Glass tubes, this set included 6D6 RF amplifier tubes. The second set of tubes were the metal octal tubes with grid caps, this set included 6K7 RF amplifer tubes. The third set used single ended metal octal tubes, and included 6SK7 RF amplifer tubes. There were also at least two different styles of dial offered, a round airplane dial, and a straight sliderule dial. My Miller High Fidelity Tuner has the single ended metal octal tubes and a sliderule dial.
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