This audion was made by McCandless for De Forest in 1913. It has a single control grid and anode but a double Hudson filament.
The base of the original box.
Thanks to Joe Gruber for sending the images.
The balloon envelope is 50 mm in diameter and, excluding the base, is 76 mm tall.
Reference: Joe Gruber. Type Audion was first introduced in 1911. See also 1911 adverts.
Updated September 22, 2020.