The Z14 is a variable μ RF pentode for dry battery operation used for domestic broadcast receivers at RF or as an IF amplifier. The filaments had to have the lowest possible consumption due to the cost of the dry batteries.
The Osram paper label.
Looking under the outer perforated screen.
The wide glass tube envelope is 29 mm diameter, and excluding the IO base pins, is 78 mm tall.
References: Datasheet, 1040 & 1043. Type Z14 was first introduced in 1940.