Two, RCA 5691 tubes, the long life/high reliability 6SL7GT. Red micanol bases, gery plates, reinforcing rods. The 5691 is of course the ruggedized, low microphonics, low noise, high reliability, long-life version of the 6SL7GT tube and can be used in applications calling for the 6SL7GT. Tested on a Hickok TV-3 military tester that has been calibrated. Firm bases, excellent silvering. Tubes are matched for dynamic gain and structure- test at 1875-1750, 1750-1625 where pass/fail is 1100 micromho. Tubes have the same exact structure inside and out, having matching date codes of "7009", the 9th week of 1970.  Based on their appearance and the test values, these tubes are either new or very lightly used.

Many other lots of tubes for sale this week.

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