Tested for mutual transconductance in Hickok 539B tube tester (minimum for
good 12AT7 = 1950 umhos). All tubes test very strong to like new. Then,
tubes were individually tested for noise and sonic performance in my Hovland
HP100 MC preamp.

(2) Pairs RCA 12AT7 black plate, square getter, red lettering, considered
one of the best and better than most standard Euro brands according to Hong
Kong Tube Audio Group afficionados. Pr. 1 tests at: 3000/2800; 3000/3180,
$20.00/pr. Pr. 2: 3500/3550; 3350/3850, $40.00/pr.

Pr. Sylvania 6679 = ruggedized 12AT7, yellow lettering, flat black plates
crimped on both sides, round getters, tubes test at: 3520/3480; 2950/4280.
$25.00/pr.

(3) Sylvania 12AT7WA, triple mica, gray plates, tubes test at: 4120/5000;
3900/4100; 4400/3850. $15.00 ea.

(2) GE 12AT7WA 6201, gray plates, additional support rods, round getters,
3250/3200; $12.00 ea., (1) with triple mica, tests at: 4000/3500, $15.00.

(2) Sylvania 12AT7, black plates, green lettering, tubes test at:
3750/4080; 3400/3430, $15.00 ea.

(2) Sylvania 12AT7, gray plates, yellow lettering, tubes test at:
3100/2900; 4100/2950, $8.00/pr.