The 8425  (P/N 154-0022-07) is an RF pentode vacuum tube.

Some instruments using part 8425

Instrument Manufacturer Class Model Description Introduced
310A Tektronix Oscilloscope 310A 4 MHz oscilloscope 1959
317 Tektronix Oscilloscope 317 10 MHz 3" tube scope 1959
3A72 Tektronix Plug-in 3A72 Dual channel amplifier plug-in 1961
526 Tektronix Audio/Video 526 NTSC Vectorscope 1959
Q Tektronix Plug-in Type Q Strain gauge preamp plug-in 1960