Tyne page 308ff brings the details of history. Here the main points only: The first tubes RCA is marketing in 1920 are the detector tube UV200 with argon gas filling and the UV201 Amplifier. Manufacturer was General Electric (GE).
In 1922 GE replaces the UV201 with the UV201A, having now a thorium filament.
In August 1925 this tube comes with a new base and standardised construction (of 1923) for neutrodyne apparatus and is then called UX201A (short name 201A - which should not to be confused with the Western Electric 201A, the Myers tube 201A and the "Star Tube" 201A). Cunningham is naming the tube CX301A.
By having the tube with a shoulder type glass envelope (dome type) in 1932 the designation is changed to 01A.
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