The X64 is a heptode variable μ mixer. It was the prototype for the UK Government specification for: Navy NR67, Army ARH1 and was finally brought into the CV register as CV1280.
The etched M-OV lozenge.
With some processing the X64 can be read.
The classic envelope is 39 mm in diameter and, excluding the IO base pins, is 98 mm tall.
Reference: Data-sheet. Type X64 was first introduced in 1937. See also1937 adverts.
