The CV492 is the 12AX7 high impedance amplifier triode. The design has a high amplification factor of 100. The RCA data-sheet says the valve is suited to RC-coupled amplifiers, multivibrators and industrial control.
The face view of one anode.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 45 mm tall.
References: Data-sheet, 3002 & 1040. Type CV492 was first introduced in 1947. See also 1947 adverts.