(!!!) (Recommended Pair) 12A National Union NOS 1950 era different shape top mica (8.5ma and 8.1ma)

1 pair) 12A National Union NOS 1950 era different shape top mica

1 tube) 8.5ma Gm=1700

1 tube) 8.1ma Gm=1800

Vplate = 180V

Vgrid = -13.5V

Good Ma = 6-7ma

Good Gm = 1600-1700