This Ba triode was made by Siemens and Halske and the design dates to 1928 but still uses the older style glass rod electrode support. The base is the European telephone five pin and telephone repeater service is the probably use.
A combination of the side glass rod and supports fixed into the pinch support the anode etc.
The five pin base. The pins are solid suggesting that the holder was of the bayonet type with side loading spring cups. The Bakelite infill has a locating protrusion.
The side supports hold the anode in place. On the glass can be seen the etched Ba and the Siemens logo.
An enhanced image of the etching in the glass.
The central filament has ladder grids on either side.
The painted lettering seems to be the actual mutual conductance of 0.65 Amp.
The filament tension springs are anchored in the side glass support as are the supports for the grids.
The glass rod support.
Top view showing the inter-electrode spacing.
The balloon envelope is 48 mm in diameter and, excluding the base pins, is 106 mm tall.
Reference: Data-sheet. Type Ba was first introduced in 1928. See also1928 adverts.