1 tube) 6B4G Sylvania rebranded RCA used/very good 1953 separate plates

77.5ma and  Gm=5600  

(6B4G=6.3V filament)
(6B4G is electrically equivalent to 6A3, but 6A3 has UX-4 pin base and 6B4G has 8 pin octal base)
(The best sounding 6B4G are 1940's-1950's: Ken Rad, Tungsol, Sylvania, Raytheon)