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WE 421a - Black Plates from 1967 | WE 5998/421a - Grey Plates from 1954 | Chatham 5998 from 1960 | Tung-Sol 5998 from 1966 | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet!
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Western Electric WE 421a NOS and 5998 tube test like new - Shipping included Photo #632305 - Canuck Audio Mart
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Visual evidence Tung-Sol 5998 = Western Electric 421 | Headphone Reviews and Discussion - Head-Fi.org
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