The CV423 is a double triode and is a special variant of the commercial 25SN7GT. The specification specifies a vibration test and so this is probably a ruggedised version.
No specific Type designation is seen on the glass. The type information has been scratched onto the base. The absence of double mica sheets would suggest that this is more likely to be the commercial 25SN7GT.
The data-sheet for the 6SN7GT indicates the usage of this medium μ double triode is as an RC coupled amplifier or a TV vertical oscillator and output valve. In the latter case one anode can be run at 3.5 Watts dissipation providing the total dissipation remains at five Watts maximum.
The twin triode sections. The control grids are wound on copper supports and have heat sinks attached to the tops of thew supports.
The top mica showing the heat sinks attached to the grid supports. In total the valve anodes can dissipate 5 Watts.
Side view of one anode.
The classic envelope is 45 mm in diameter, and excluding the IO base pins is 86 mm tall.
Reference: Datasheet. Type CV423 was first introduced in 1937.