WW2 British radio box No.4

This is a WW2 British box that belonged to the Wireless 18 set.
It contained spare “valves”, but I call them lamps !
Inside of the box is covered with shock absorbent material.

Markings:
The lid has the markings on the lid that read “Case 4 Valve No.3 ZA9817”
The ZA number indicates that it special transmitting equipment.
Condition: light used / Still one of the lamps present.