A brass 4-pin base with tipped T-shaped envelope. Donor card reads: "Triode made by De Forest for the O and T Electric Company in the early 1920s. A 5 volt filament of otherwise unknown specifications ...
A plastic 5-pin base with top contact, mesh grid, S-shaped envelope. Base Stamped: "RCA Radiotron / 235"; on envelope: "RCA". Handwritten paper label - faded ...
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