This B5 exhibit shows a clean unpitted nickel base shell as well as split pin construction. Unlike our other B5 exhibits this valve has the evacuation seal at the top of the envelope.
The BTH (British Thomson-Huston Co) B5 is a triode that was released in 1923. It is designated as a general purpose valve and has an amplification factor (μ) of 7. The low filament current is indicative of a dull emitter valve. The filament rating of 2.8 Volts was chosen so that the valve could be heated by two dry cells in series. See also B5 and B5.
The balloon envelope is 37 mm in diameter and, excluding the B4 base pins, is 92 mm tall.
Reference: 1003. Type B5 was first introduced in 1923.