The 6AB4 is a single triode designed for use as a mixer, amplifier or oscillator in VHF television receivers. The heater is controlled in both voltage and current requirements so that it can be used for parallel or series heater chains.
The envelope is also marked as EC92 thus indicating that the Types are identical.
The triode section is small in relation to the 18 mm diameter of the envelope, only 3.5 mm front to back. The grid can be seen to be wound on copper supports.
The total width of the anode is 10 mm.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 49 mm tall.
References: Datasheet & 1040. Type 6AB4 was first introduced in 1952.