Up for sale here is this used GE Made in USA 6201. This is a 12AT7 variant, and is from the late 1950s or early 1960s. This is a triple mica tube. I tested it on my B&K 747B tube tester, and it tested at 79/63, with no shorts or grid emissions, on a scale of 0-120, where 65 is minimum good and most 12AT7s test in the 50-75 range.
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