The KC1 from Valvo is a 1930s audio amplifier triode for battery operation.
The envelope has a shoulder but in this case it is not used for firmly securing the top mica sheet to the envelope. In fact only one of the four corners of the two mica strips actually touches the glass.
The grid extends above and below the anode. The filament tension spring is hidden by the mica strips.
The classic envelope is 40 mm in diameter, and excluding the Ct8 base pins is 89 mm tall.
References: Data-sheet, 1040 & 1043. Type KC1 was first introduced in 1936. See also1936 adverts.
