This new-old-stock-testing, physically matched pair of RCA 6L6GC output tubes was tested on our Maxi-Matcher with 400 volts on the plates and a bias of -48 volts for shorts, gas and transconductance. There were no shorts or gas and they tested as follows:
Tube One: Tube Two:
Transconductance: 2730 micromhos Transconductance: 2960 micromhos
Plate Current Draw: 70.9 milliamps Plate Current Draw: 82 milliamps
(New US-made 6L6GCs typically test with plate current from the low 20s to mid 30s with transconductance from 2200 micromhos or so.) These tubes test substantially above spec for plate current draw and are not matched for plate current. If you can bias each tube separately, they will be fine and this is the reason I ran them in a single-ended amp.
These tubes have bottom, double-D getters; coarsely-crenelated round top and bottom spacers; anode radiators for cooler operation and longer life; good flashing (for this tube variety) and 043 C and mc date codes, respectively.
I am playing them in my Musical Paradise MC-3 single-ended integrated amplifier with The Eagles' seminal "Hotel California" album and they sound terrific. These tubes have great bass and sparkling highs and Glenn Frey's voice is warm and clear as a bell.
Please note that Tube Two is showing some color (Picture Seven). I let them run all day and things remained status quo.