(!!) (BEST PAIR) 6C8G National Union and Ken Rad NOS same build 1950 era (3.8/3.7ma and 3.9/3.5ma) (closely matched)
(!!) (slightly microphonic pair) JAN-6SL7GT=VT-229 RCA NOS and like new 1940's (2.5/2.4ma and 2.4/2.6ma) 1-3% matched
(!) 6SL7GT RCA burgundy base NOS 1951 (1.7/1.8ma)
(BEST SINGLE) 6C8G RCA Radiotron NOS 1940's (3.8/3.9ma) 1-3% section balance
6C8G CBS NOS 1950's (like RCA) (3.7/4.1ma)
6C8G National Union NOS 1950 era (3.6/5.8ma)
6C8G=VT-163 Tungsol round black plates like new 1940's (3.1/3.2ma) 1-2% section balance
