This is a rare Marconi component from a marine wireless telegraphy installation circa 1918. Manufactured by the "Marconi's Wireless Telegraph Co. Ltd" and referred to as "Local Oscillator". It consists of a set of plug-in coils covering a range of wavelengths which are coupled through a variometer arrangement to a tuning variable capacitor. The V24 valve provides the oscillatory circuit. The plug-in coil that comes with this set covers the wavelength ranges of 400-900 and 700-1800 metres. 

The photo of picture 10 comes from Stanley, R.  "Text-Book on Wireless Telegraphy  Volume II Valves and Valve Apparatus" published ~1919. It gives a long description of  the Type 121 oscillator in directional receivers.   In picture 9, a photo of a ship’s communications room shows the oscillator in the right hand side of the lowest row under the group of three instruments labelled "Receiver".  

The V24 Marconi valve has a good filament. This piece is in exceptionally good cosmetic and hardware condition.

Prepared to send worldwide.