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 solid screen hides the inner components.
The Osram brand marked by the paper label.
The wide glass tube envelope is 29 mm diameter, and excluding the IO base pins, is 80 mm tall.
References: Data-sheet, 1040 & 1043. Type Z14 was first introduced in 1940. See also1940 adverts.