The E1111 experimental valve from the M-OV labs is a tetrode. It is battery powered as is confirmed on the label. The interesting thing is the presence of rods at each end which are probably used to mop-up secondary electrons and thus act as beam plates.
This exhibit is serial number 73.
The filament voltage is given as both 1.4 Volts and 2.8 Volts and therefore two 1.4 Volts strands in series. Looking at the pinch end shows two separate filament terminations and there are two tension springs at the top.
The dome and where the filament strands pass through the top mica the inner grids can be seen.
The wide glass tube envelope is 28 mm in diameter, and excluding the IO base pins is 74 mm tall.
Updated February 03, 2017.