10 Sylvania "engraved base" 1930's NOS 

29ma

Gm=2000

Vplate=300V

Vgrid=-15V

Good mA range 20-30ma

Good Gm range 1700-2000 

General Information

(Filament=7V @ 1.2A, Vplate=220V, Vgrid=-7V, Iplate=25ma, Mu=6, Rp=6Kohms)

(The VT-25 is built exactly the same as a VT-52, but the plate and grid are spaced  differently yielding ifferent Mu factors and plate resistance)