The A211 carries the Helikon brand. Helikon was a Dutch company that became part of the Philips group. This battery triode has a horizontal cylindrical anode in the same design format as the first hard valves.
The identification is etched into the glass dome and the double image is formed from the reflection from the inner surface of the glass that is mirror like due to the gettering.
The horizontal anode with helical grid and intact filament. On test the filament took 0.022 Amps at 2.0 Volts.
Here the thoriated tungsten filament can be seen clamped in a fold at the top of the support wire.
This enhanced image shows the filament a little better.
The balloon envelope is 45 mm in diameter and, excluding the B4 base pins, is 83 mm tall.
Reference: Observation. Type A211 was first introduced in 1937. See also1937 adverts.