Two, NEW in box, Philco branded- Sylvania manufactured 6SN7GTB tubes. These tubes were manufactured by Sylvania, as evidenced by inspection, as well as the presence of the "312" manufacturers code on the base- which uniquely identifies Sylvania as the original manufacturer. Red printed logo bases, grey, angled T-plates, chrome dome silvering. Tested on a Hickok TV-3 military tester that has been calibrated, just to make sure. Firm bases, excellent silvering. Tubes are matched for dynamic gain and structure- test at 3375-3375 and 3375-3250 where pass/fail is 1625 micromho.  They have the same structure inside and out, having date codes of "57-52" and "58-39", the 52nd week of 1957 and the 39th week of 1958. 

Many other lots of tubes for sale this week.

Shipping is free within the continental US. Elsewhere- exact postage only, no packing feee