This single tube was manufactured in the Amperex Hicksville, NY plant in November,1958. It bears code 7LK *8K (see 3rd photo below) and measured 1170/1225 which is less than a 5% triode to triode variance.It was used solely as the input tube in a Conrad Johnson Premier 140 amp for 60 hours. I know the precise hours because I was breaking in new Teflon capacitors on the amp and tracked both the tubes used and the hours they ran as the amp was breaking in. Of the literally dozens of different tube types used in the amp this was my favorite. The photo below is the tube as new. The ones that follow it show the effect putting on and taking off on the chalk lettering of the two silicon O-rings that Conrad Johnson supplied for the input tube. The price includes PayPal fees and USPS Priority Mail shipping. If you have any questions just ask. Thanks.
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