The P2018 is an audio power triode with a 20 Volt 0.18 Amp heater designed for series heater chains. It requires a load impedance of 6,000 Ω, a cathode resistor of 750 Ω and will deliver 900 mW of output.
We also have the R2018 in the museum. The two look identical, and share the same heater requirements, but the R version is a low power general purpose signal processor.
The dome carries all the identification. Barium tube is used as a branding device and does not refer to the older Azide process.
The construction looks to be identical to the R2018 and it is possible that under spec P2018s may have been the source of the R2018.
A μ-Tracer plot of the characteristic curves for this exhibit.
The classic envelope is mm in diameter, and excluding the base pins is mm tall.
Reference: 1043. Type P2018 was first introduced in 1934.