The Type 58 is a variable μ RF and IF pentode for use in superhet radio receivers and dates from the late 1930s. Electrically it is identical to the 6D6 and the 6U7G.
The top cap and the frosted glass has a ground glass feel.
Above the internal coating can be seen the cylindrical anode and the three wire grids. The while of the oxide coated cathode is also seen in the image.
The classic envelope is 39 mm in diameter, and excluding the UX6 base pins is 103 mm tall.
References: Data-sheet, 1040 & 1043. Type 58 was first introduced in 1936. See also1936 adverts.
