The 1S5 is a diode pentode valve was designed for battery portable radio receivers. This short grid base pentode was designed with particular reference to AF voltage amplification. The 1.4 Volt filament is to be run from a dry cell and the 90 Volt anode rating matches standard HT batteries.
The bright nickel anode is oval in shape and hides the grids. The filament is a single strand that runs from the base connections, through the electrodes and out of the top mica to a spring support at the top of the valve.
Here we have another version of the 1S5, this time made for the Canadian General Electric Company.
The three grid supports can be seen above the top mica. The micas themselves have the points facing downwards showing the interference fit to the glass tube that holds the electrodes firmly in place.
As well as showing the wire grids within the anode this image shows the single strand filament passing through the top mica and then between the plates of the diode anode.
The thin glass tube envelope measures 17 mm in diameter and the excluding the B7G base pins, is 43 mm tall.
References: Datasheet, 3002 & 1043. Type 1S5 was first introduced in 1938.