(!!) (Pair) 37 Sylvania 1940 era used/good no printing (6.6ma and 6.5ma) (Same Gm) 1-2% matched

1 pair) 37 Sylvania 1940 era used/good no printing in white boxes

1 tube) 6.5ma Gm=900

1 tube) 6.6ma Gm=900

Test parameters:

Vplate=250V

Vgrid=-18V

Iplate good range 6.5-8ma

Gm=1000-1100

(Filament=6.3V @ 300ma, many think the 37 sounds better than the 76)