The '1938' is part of the equipment description.
The item is not WW2, and certainly not from 1938 - RDF and A.I,, later to become known as RADAR, was very much in its infancy in the late 1930s and early 1940s, with the first proper airborne use being in late 1940, with a very basic, and not very reliable 'detection' radar for night fighters.
The type of equipment your part comes from was no developed until after WW2.