The VO13 is an octode frequency changer. The Mullard FC13C is a close match but not identical.
In use the local oscillator would be formed between the cathode and second grid. The signal usually being added at g4, the top cap. Grids three and five formed the screening grids.
Such golden external metallised valves can be seen in radio sets from the mid1930's to early 1940's.
The reverse of the envelope is plain gold coloured zinc paint.
The top cap and multiple grid supports.
The classic envelope is 46 mm in diameter and, excluding the B7 base pins, is 113 mm tall.
Reference: 1043. Type VO13 was first introduced in 1935. See also1935 adverts.
