This exhibit has lost all identification. The style of the base cap and envelope all indicate a Dario product from the 1920s. The Universal Bivolt looks identical.
The anode is horizontal and the four visible supports are typical of triodes of the period with a single V for the filament. Powering the filament at 1.8 Volts gave a consumption of exactly 0.1 Amp. Looking at the advert gives only two possible Types - Universal or Resistron.
The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 87 mm tall.
References: Observation and test.
Absolute Maximum Operating Conditions¶
Updated November 20, 2017.