This is a Marconi Q valve.
The most striking feature of this triode is the wire mesh cage grid. The grid is made of longitudinal wires with interwoven helical wire and all supported on a rectangular wire frame. The filament is not clear but is a single strand filament running the length of the valve and tensioned by a spring. The filament is complete, and therefore this valve will work. The anode is a plane metal cylinder taken to one of the side connections.
This exhibit was purchased complete with original wooden box into which it is fastened with a length of wire.
Above can be seen the lid of the box. The caption, written long ago, sums up this little valve. We believe that the G2RN is a reference to an amateur radio callsign.
The thin glass tube envelope is 15 mm in diameter and, excluding the base pins, is 70 mm tall. Across the side pips measures 23 mm.
References: 1003 & 1005. Type Q was first introduced in 1916.
Updated April 25, 2013.