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 etched lettering shows the country of origin as West Germany but the reverse side has the Sylvania name in yellow.
The small triode centred in the glass envelope.
Part of the Sylvania name and the anode side flange stitched and fixed through the mica sheets.
The gap in the anode side wall reveals the grid.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Datasheet & 1040. Type 6AB4 was first introduced in 1952.