Two 12AT7 / ECC81 tubes - just tested.One is labled Penta Labs - Made in USA - and tests 5100/5600 where 5400 is considered new. It has short plates, copper support rods, a very large halo getter and on the side opposite the label are the numbers 9007. Maybe Sylvania manufacture? The other is Ei Yugoslavian manufacture and labeled VTL. It has longer plates, a halo getter and the other marks are 3A1 ?1B. It tests 4000/4300. Both are labeled 12AT7WA Both were tested on a calibrated Triplett 3444 analyzer.
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