Pictures:

Details:
Ionization tube, suitable for vacuum measurements up to 10 ^ -11 torr, corresponding to a measured current (ion current) of up to 10 ^-13A
Datasheet:
Filament 5 Volts Vf / If: 1 Amp / -: Direct /
Uik =-30V
Ug = 180 V
Ig = 0.2 mA
Links:
http://www.radiomuseum.org/tubes/tube_mr04.html