The Ediswan LF210 is a general purpose low frequency triode - this is stated on the envelope. The envelope also gives the amplification factor and anode AC impedance.
The bright anode and filament centre support.
The BVA logo etched into the glass.
The balloon envelope is 39 mm in diameter and, excluding the B4 base pins, is 85 mm tall.
Reference: Data. Type LF210 was first introduced in 1927. See also1927 adverts.
