The chrome cap looks to be original, but the bulb holder maybe not. These were originally Bakelite, though it’s not beyond the realms of possibility that brass was used later. Anyway, c.1937 these should be double fittings with illumination for the base. If you’re using the lamp now I’d suggest adding an earth connection to the metalwork for safety (otherwise with the brass fitting the whole cap could become live if a wire detached itself from the bulb socket).
If the threaded tube is long enough, you may also be able to add a bulb holder on the underside to light the interior as per the catalogue. If lighting the interior, I recommend the use of LED bulbs as they run fairly cool and will minimise the risk of cracking due to heat stress.