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This De Forest Audion valve is a very early production type.

The filament is a single strand formed into two loops. It is probably pure tungsten or tantalum and would be bright like a filament lamp in operation. The grid is a crude zig zag of thick wire, and the anode is a rectangular nickel plate. The whole construction being of parallel planes. The filament connects to an Edison screw base, known as a candelabra cap. The grid and anode connect at the top via silk covered wires.

The balloon envelope is 48 mm in diameter and, excluding the base pins, is 90 mm tall.

Reference: ¹⁰⁴⁷. Type Audion was first introduced in 1911. See also 1911 adverts.