The 8FQ7 is a medium-mu double triode. The design purpose was for the line and frame oscillators in television receivers. The 8FQ7 was designed for 450 mA series heater chains. The 6FQ7 has a heater rating of 6.3 Volts at 600 mA making it suitable for parallel heaters or for sets using the 600 mA series standard. The 12FQ7 is rated at 12.6 Volts and 300 mA.
The NEC identification is printed onto the glass.
The triode sections. Each has the control grid wound on copper supports and flanged anodes that offer greater area for heat dissipation that a plain box anode.
One section seen end on.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 57 mm tall.
Reference: Data-sheet. Type 8FQ7 was first introduced in 1965.