Raytheon black plate 12AX7. Matched trio; same construction. While the brands differ (see picture), I guarantee the three sound identical.
Hickok TV10 ( 1,000 in min; 2,000-2200 is NOS) Gm:
On an EICO 666 (120 is NOS; 140 is the meter max):
These sell for $120 each at Tube World (a superior vendor, BTW), and an incredible $200 per tube at Tube Depot (also an excellent provider).
Wonderfully linear sound, while retaining warmth and focus in the mids. Long-lasting and quiet.
$120 shipped in CONUSA by USPS Priority with tracking.