This exhibit is a spherical Audion fitted with the Hudson filament.
The filament connects to the base with the grid and anode brought out to wires at the top.
A close-up of the twin pinches and electrodes. The anode and grid are duplicated either side of the twin filament. Here one filament strand is open circuit and the other has the tantalum wire wrap of the Hudson filament. The grid is in the original De Forest style of a grid iron.
Face view of one of the anode plates.
The electrodes seen side on. The wide space between grid and filament will confer a low amplification but was probably done to minimise the risk of filament shorting to one side of the grid. Note the tantalum wire wrap on the filament.
A close-up. The tantalum wire seems to have been compressed to hold it in place on the tungsten filament.
The balloon envelope is 52 mm in diameter, and including the candelabra base is 85 mm tall.
Reference: 1047. Type Audion was first introduced in 1911. See also1911 adverts.