The 30C1 from Mazda is from the era of VHF television in the 1950s and early 1960s. The valve is a triode pentode designed to function as a mixer and oscillator in the tuner. The local oscillator has to generate five Volts peak to peak.
The 30C1 is sensibly equivalent to the PCF80 but slight differences do exist. Mazda made both types.
The triode section.
A genuine UK made valve. Note the screen below the bottom mica.
The relative sizes of the two sections.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins is 46 mm tall.
References: Data-sheet & 1040. Type 30C1 was first introduced in 1954.